I am constructing a calculator and this is my html for the calculator
HTML
<div id=”calculator”>
<input type="text" name="display" id="display" disabled>
<div class="first-row">
<input type="button" name="operator" value="+" action="add">
<input type="button" name="operator" value="-" action="subtract">
<input type="button" name="operator" value="*" action="multiple">
<input type="button" name="operator" value="/" action="divide">
</div>
<div class="second-row">
<input type="button" class="number" value="7">
<input type="button" class="number" value="8">
<input type="button" class="number" value="9">
</div>
<div class="third-row">
<input type="button" class="number" value="4">
<input type="button" class="number" value="5">
<input type="button" class="number" value="6">
</div>
<div class="fourth-row">
<input type="button" class="number" value="1">
<input type="button" class="number" value="2">
<input type="button" class="number" value="3">
</div>
<div class="fifth-row">
<input type="button" class="number" value="0" onclick="numberPress('0')">
<input type="button" class="operator" value="=">
</div>
</div>
<script type="text/javascript" src="../javascript/calculator.js"></script>
So in my javascript code, it checks if the button clicked is a operator, then if it is, then it prints out "operator" in the console.
Javascript
const calculator = document.getElementById("calculator")
calculator.addEventListener("click", e => {
if (e.target.matches("input")) {
key = e.target
name = e.target.name
if(name == "operator") {
console.log("operator")
}
}
})
The problem is that for the first line, it does not find the calculator id and it stores null in calculator. So, I tried putting the javascript in the same file, but still it does not work.
Any help will be very appreciated
You are not using this character "
You are using this character ”
So you are writing ”calculator” instead of "calculator" in your HTML
You must use plain quote marks in HTML
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I am making a simple calculator with vanilla.js. However, I am having difficulty on creating the functionalities. I can get to display the number when click, but not when I click multiple times or delete that value on click. i tried addeventlistener but i always get an Type Error "addeventlistener not a function".. if you have any recommended website or tutorial to better understand vanilla, please point it.. thanks in advance
var result = document.querySelector('#result');
var clear = document.querySelector('#delete');
var backSpace = document.querySelector('.backspace');
var numbers = document.querySelectorAll('.input-btn');
var operators = document.querySelector('.operator-right');
var equalBtn = document.querySelector('.equal-btn');
function insert(num) {
result.value = num;
}
<div class="container">
<div class="calc">
<div class="result">
<input class="input-btn__result" id="result" value="0">
</div>
<div class="btns">
<input class="clear" id="delete" type="button" onClick="clear()" value="C">
<input class="backspace" type="button" name="" value="<">
<input class="input-btn__divide operator-right" type="button" name="" value="/">
<input class="input-btn" type="button" onClick="insert(1)" value="1">
<input class="input-btn" type="button" onClick="insert(2)" name="" value="2">
<input class="input-btn" type="button" onClick="insert(3)" name="" value="3">
<input class="input-btn operator-right" type="button" name="" value="*">
<input class="input-btn" type="button" onClick="insert(4)" name="" value="4">
<input class="input-btn" type="button" onClick="insert(5)" name="" value="5">
<input class="input-btn" type="button" onClick="insert(6)" name="" value="6">
<input class="input-btn operator-right" type="button" name="" value="+">
<input class="input-btn" type="button" onClick="insert(7)" name="" value="7">
<input class="input-btn" type="button" onClick="insert(8)" name="" value="8">
<input class="input-btn" type="button" onClick="insert(9)" name="" value="9">
<input class="input-btn operator-right" type="button" name="" value="-">
<input class="input-btn" type="button" onClick="insert('.')" name="" value=".">
<input class="input-btn" type="button" onClick="insert(0)" name="" value="0">
<input class="equal-btn" type="button" name="" value="=">
</div>
</div>
</div>
There are multiple ways of doing what you want to do. Stack Overflow is not a place to ask for recommendations on resources for learning vanilla JS (if you google you can find multiple good resources and pick the one you like best). As Alvin already mentioned in his answer, you definitely want to learn more about how to use addEventListener.
This is how I'd do it using your HTML (with one important exception: I've eliminated all your onClick HTML attributes -- it's best to separate your JavaScript code from your HTML structure):
const result = document.getElementById('result'),
btns = document.querySelector('div.btns');
/*
calculandum here is the previous number,
to be used with the math operation (+, -, /, *)
*/
let calculandum = '';
// addEventListener to all your buttons
for (let child of btns.children) {
child.addEventListener('click', insert);
}
function insert(e) { // e is the event; e.target is the HTML element; e.target.value is this element's value
let btnValue = e.target.value;
switch (btnValue){
case 'C':
result.value = '0';
calculandum = '';
break;
case '<':
if (result.value) result.value = result.value.slice(0,-1);
if (result.value === '') result.value = '0';
break;
case '*':
if (result.value) { // result.value will be '' after an operator is clicked, as can be seen in the next lines
calculandum += result.value + '*';
result.value = '';
}
break;
case '=':
calculandum += result.value;
result.value = eval(calculandum);
calculandum = '';
break;
default:
result.value === '0' ? result.value = btnValue : result.value += btnValue;
}
}
<div class="container">
<div class="calc">
<div class="result">
<input class="input-btn__result" id="result" value="0">
</div>
<div class="btns">
<input class="clear" id="delete" type="button" value="C">
<input class="backspace" type="button" name="" value="<">
<input class="input-btn__divide operator-right" type="button" name="" value="/">
<input class="input-btn" type="button" value="1">
<input class="input-btn" type="button" name="" value="2">
<input class="input-btn" type="button" name="" value="3">
<input class="input-btn operator-right" type="button" name="" value="*">
<input class="input-btn" type="button" name="" value="4">
<input class="input-btn" type="button" name="" value="5">
<input class="input-btn" type="button" name="" value="6">
<input class="input-btn operator-right" type="button" name="" value="+">
<input class="input-btn" type="button" name="" value="7">
<input class="input-btn" type="button" name="" value="8">
<input class="input-btn" type="button" name="" value="9">
<input class="input-btn operator-right" type="button" name="" value="-">
<input class="input-btn" type="button" name="" value=".">
<input class="input-btn" type="button" name="" value="0">
<input class="equal-btn" type="button" name="" value="=">
</div>
</div>
</div>
This should work for multiplications, from this example you can code the rest of the operations. You can also note I've eliminated most of your vars because they weren't doing anything. One final note is that I'd definitely rethink how you're using classes for your HTML elements. For example, classes should be used for multiple elements, you can use IDs for just one element (so, classes calc and btns maybe should be IDs).
You can add a class name for input buttons which for insert function, and then use addEventListener to add event.
var result = document.querySelector('#result');
var clear = document.querySelector('#delete');
var backSpace = document.querySelector('.backspace');
var numbers = document.querySelectorAll('.input-btn');
var operators = document.querySelector('.operator-right');
var equalBtn = document.querySelector('.equal-btn');
var insertBtns = document.querySelectorAll('.insert-btn');
function insert(e) {
result.value = e.target.value;
}
for (var i = 0; i < insertBtns.length; i++) {
insertBtns[i].addEventListener('click', insert);
}
<div class="container">
<div class="calc">
<div class="result">
<input class="input-btn__result" id="result" value="0">
</div>
<div class="btns">
<input class="clear" id="delete" type="button" onClick="clear()" value="C" >
<input class="backspace" type="button" name="" value="<">
<input class="input-btn__divide operator-right" type="button" name="" value="/">
<input class="input-btn insert-btn" type="button" value="1">
<input class="input-btn insert-btn" type="button" name="" value="2">
<input class="input-btn insert-bt" type="button" name="" value="3">
<input class="input-btn operator-right" type="button" name="" value="*">
<input class="input-btn insert-btn" type="button" name="" value="4">
<input class="input-btn insert-btn" type="button" name="" value="5">
<input class="input-btn insert-btn" type="button" name="" value="6">
<input class="input-btn operator-right" type="button" name="" value="+">
<input class="input-btn insert-btn" type="button" name="" value="7">
<input class="input-btn insert-btn" type="button" name="" value="8">
<input class="input-btn insert-btn" type="button" name="" value="9">
<input class="input-btn operator-right" type="button" name="" value="-">
<input class="input-btn insert-btn" type="button" name="" value=".">
<input class="input-btn insert-btn" type="button" name="" value="0">
<input class="equal-btn" type="button" name="" value="=">
</div>
</div>
</div>
I have a simple calculator with 2 inputs, and when I click on button I want to check if one of inputs is focused and if yes to enter that number.
But when I click on button I lose focus on inputs and get it on that button.
let activeElement = document.activeElement;
function numClick(number){
console.log("Num clicked=" + number);
let tempNumber="";
tempNumber = activeElement.value;
tempNumber = tempNumber + number;
activeElement.value=tempNumber;
}
<input id = "num1" type="text" name="num1" value="">
<span id="operacija"></span>
<input id = "num2" type="text" name="num2" value="">
<span>=</span>
<span id="rezultat">0</span>
<br><br>
<input type="button" onclick="clearIt() "value="C">
<input type="button" onclick="operationClick('/')"value="/">
<br>
<input type="button" onclick="numClick(7)" value="7">
<input type="button" onclick="numClick(8)" value="8">
<input type="button" onclick="numClick(9)" value="9">
<input type="button" onclick="operationClick('*')"value="*">
<br>
<input type="button" onclick="numClick(4)" value="4">
<input type="button" onclick="numClick(5)" value="5">
<input type="button" onclick="numClick(6)" value="6">
<input type="button" onclick="operationClick('-')"value="-">
<br>
<input type="button" onclick="numClick(1)" value="1">
<input type="button" onclick="numClick(2)" value="2">
<input type="button" onclick="numClick(3)" value="3">
<input type="button" onclick="operationClick('+')" value="+">
<br>
<input type="button" onclick="numClick(0)" value="0">
<input type="button" onclick="calculate()" value="=">
<br>
<script type="text/javascript" src="zadatak1.js"></script>
I am not using any framework, just JS...
This is just a working sample of the suggestion given by Teemu. So credit there.
We add a focus event to our input controls and record the last focused control.
document.addEventListener('DOMContentLoaded', function() {
document.querySelector('#num1').addEventListener('focus', setLastElement);
document.querySelector('#num2').addEventListener('focus', setLastElement);
});
var lastInputElement;
const setLastElement = (event) => {
lastInputElement = event.target;
console.log(event.target);
};
let activeElement = document.activeElement;
function numClick(number){
if (lastInputElement === undefined) return;
console.log("Num clicked=" + number);
let tempNumber="";
tempNumber = lastInputElement.value;
tempNumber = tempNumber + number;
activeElement.value=tempNumber;
}
<input id = "num1" type="text" name="num1" value="">
<span id="operacija"></span>
<input id = "num2" type="text" name="num2" value="">
<span>=</span>
<span id="rezultat">0</span>
<br><br>
<input type="button" onclick="clearIt() "value="C">
<input type="button" onclick="operationClick('/')"value="/">
<br>
<input type="button" onclick="numClick(7)" value="7">
<input type="button" onclick="numClick(8)" value="8">
<input type="button" onclick="numClick(9)" value="9">
<input type="button" onclick="operationClick('*')"value="*">
<br>
<input type="button" onclick="numClick(4)" value="4">
<input type="button" onclick="numClick(5)" value="5">
<input type="button" onclick="numClick(6)" value="6">
<input type="button" onclick="operationClick('-')"value="-">
<br>
<input type="button" onclick="numClick(1)" value="1">
<input type="button" onclick="numClick(2)" value="2">
<input type="button" onclick="numClick(3)" value="3">
<input type="button" onclick="operationClick('+')" value="+">
<br>
<input type="button" onclick="numClick(0)" value="0">
<input type="button" onclick="calculate()" value="=">
<br>
<script type="text/javascript" src="zadatak1.js"></script>
You can do something like this:
var activeInput = ""
function inputClick(input){
activeInput = input;
}
function numClick(number){
document.getElementById(activeInput).value += number;
}
<input id="num1" type="text" name="num1" value="" onclick=inputClick('num1')>
<span id="operacija"></span>
<input id="num2" type="text" name="num2" value="" onclick=inputClick('num2')>
<span>=</span>
<span id="rezultat">0</span>
<br><br>
<input type="button" onclick="clearIt() "value="C">
<input type="button" onclick="operationClick('/')"value="/">
<br>
<input type="button" onclick="numClick(7)" value="7">
<input type="button" onclick="numClick(8)" value="8">
<input type="button" onclick="numClick(9)" value="9">
<input type="button" onclick="operationClick('*')"value="*">
<br>
<input type="button" onclick="numClick(4)" value="4">
<input type="button" onclick="numClick(5)" value="5">
<input type="button" onclick="numClick(6)" value="6">
<input type="button" onclick="operationClick('-')"value="-">
<br>
<input type="button" onclick="numClick(1)" value="1">
<input type="button" onclick="numClick(2)" value="2">
<input type="button" onclick="numClick(3)" value="3">
<input type="button" onclick="operationClick('+')" value="+">
<br>
<input type="button" onclick="numClick(0)" value="0">
<input type="button" onclick="calculate()" value="=">
<br>
If you are ready to use Jquery, then you can try this code
let activeElement = document.activeElement;
var prevFocus;
$('input[type="text"]').focus(function() {
prevFocus = $(this);
});
function numClick(number){
console.log("Num clicked=" + number);
let tempNumber="";
tempNumber = activeElement.value;
tempNumber = tempNumber + number;
activeElement.value=tempNumber;
number= prevFocus.val() +''+ number
prevFocus.val(number)
prevFocus.focus()
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<input id = "num1" type="text" name="num1" value="">
<span id="operacija"></span>
<input id = "num2" type="text" name="num2" value="">
<span>=</span>
<span id="rezultat">0</span>
<br><br>
<input type="button" onclick="clearIt() "value="C">
<input type="button" onclick="operationClick('/')"value="/">
<br>
<input type="button" onclick="numClick(7)" value="7">
<input type="button" onclick="numClick(8)" value="8">
<input type="button" onclick="numClick(9)" value="9">
<input type="button" onclick="operationClick('*')"value="*">
<br>
<input type="button" onclick="numClick(4)" value="4">
<input type="button" onclick="numClick(5)" value="5">
<input type="button" onclick="numClick(6)" value="6">
<input type="button" onclick="operationClick('-')"value="-">
<br>
<input type="button" onclick="numClick(1)" value="1">
<input type="button" onclick="numClick(2)" value="2">
<input type="button" onclick="numClick(3)" value="3">
<input type="button" onclick="operationClick('+')" value="+">
<br>
<input type="button" onclick="numClick(0)" value="0">
<input type="button" onclick="calculate()" value="=">
<br>
This is sample code update. I have kept a track of the last focused on input and changed the text accordingly. I am guessing this is what you asked for. You can write the methods to control the value of the input fields accordingly.
<!-- Added an extra method to remember the last focus, we pass the element as the function param: -->
<input id="num1" type="text" name="num1" value="" onclick='updateFocus(num1)'>
<span id="operacija"></span>
<input id="num2" type="text" name="num2" value="" onclick='updateFocus(num2)'>
<span>=</span>
<span id="rezultat">0</span>
<br><br>
<input type="button" onclick="clearIt() " value="C">
<input type="button" onclick="operationClick('/')" value="/">
<br>
<input type="button" onclick="numClick(7)" value="7">
<input type="button" onclick="numClick(8)" value="8">
<input type="button" onclick="numClick(9)" value="9">
<input type="button" onclick="operationClick('*')" value="*">
<br>
<input type="button" onclick="numClick(4)" value="4">
<input type="button" onclick="numClick(5)" value="5">
<input type="button" onclick="numClick(6)" value="6">
<input type="button" onclick="operationClick('-')" value="-">
<br>
<input type="button" onclick="numClick(1)" value="1">
<input type="button" onclick="numClick(2)" value="2">
<input type="button" onclick="numClick(3)" value="3">
<input type="button" onclick="operationClick('+')" value="+">
<br>
<input type="button" onclick="numClick(0)" value="0">
<input type="button" onclick="calculate()" value="=">
<br>
<script>
var activeElement;
// Updating the current focused on input field:
function updateFocus(input) {
activeElement = input;
console.log("The active element is: +" + activeElement);
}
// Ensuring the number sent on click event is added to the current input box.
function numClick(number) {
// If a button pressed before focusing on any of the inputs:
if (activeElement == null) return;
console.log("Num clicked: " + number);
var tempText = activeElement.value;
tempText += number;
activeElement.value = tempText;
}
</script>
I need help with my virtual keyboard, On my keyboard there is a DIV that i use to make button value="MAG" work in javascript but i'm using the same DIV to make the keyboard work and write but using one Div with the same id="Div1" doesn't work for me ... so i have to chose between ((Writing using the keyboard .... or changing the keyboard from MAG to MIN )) not both !! .... here is my code and and as you can see you can only write using the keyboard but you can not use MAG button .... i'm sorry for my bad English ...
<html>
<head>
<style type="text/css">
#Div1{
display: block;
}
#Div2 {
display: none;
}
.divs
{
width: 50px;
height: 50px;
border: 1px solid #000;
}
</style>
<style type="text/css">
*{margin:0;padding:0;}
*{margin:0;padding:0;}</style>
<script>
(function() {
'use strict';
var i,c;
function init(){
/* get all the input elements within the div whose id is "keyboard */
i=document.getElementById('Div1').getElementsByTagName('input');
/* loop through all the elements */
for(c=0;c<i.length;c++) {
/* find all the the input type="button" elements */
if(i[c].type==='button') {
/* add an onclick handler to each of them and set the function to call */
i[c].addEventListener('onclick',makeClickHandler(c));
}
}
/* this is the type="reset" input */
document.getElementById('clear').onclick=function() {
/* remove all the characters from the input type="text" element */
document.getElementById('text').value='';
}
}
function makeClickHandler(c) {
i[c].onclick=function() {
/* find the non-text button which has an id */
if(i[c].id==='back') {
/* remove last character from the input the type="text" element using regular expression */
document.getElementById('text').value=
document.getElementById('text').value.replace(/.$/,'');
}
/* find the text buttons */
else {
/* add characters to the input type="text" element */
document.getElementById('text').value+=this.value.toLowerCase();
}
};
}
window.addEventListener?
window.addEventListener('load',init,false):
window.attachEvent('onload',init);
})();
</script>
</head>
<body>
<div id="Div1">
<div>
<input value="1" type="button">
<input value="2" type="button">
<input value="3" type="button">
<input value="4" type="button">
<input value="5" type="button">
<input value="6" type="button">
<input value="7" type="button">
<input value="8" type="button">
<input value="9" type="button">
<input value="0" type="button">
<input value="Borrar" type="button">
</div><div>
<input value="q" type="button">
<input value="w" type="button">
<input value="e" type="button">
<input value="r" type="button">
<input value="t" type="button">
<input value="y" type="button">
<input value="u" type="button">
<input value="i" type="button">
<input value="o" type="button">
<input value="p" type="button">
<input value="`" type="button">
<input value="+" type="button">
</div><div><input value="a" type="button">
<input value="s" type="button">
<input value="d" type="button">
<input value="f" type="button">
<input value="g" type="button">
<input value="h" type="button">
<input value="j" type="button">
<input value="k" type="button">
<input value="l" type="button">
<input value="ñ" type="button">
<input value="´" type="button">
<input value="ç" type="button">
</div><div>
<input value="<" type="button">
<input value="z" type="button">
<input value="x" type="button">
<input value="c" type="button">
<input value="v" type="button">
<input value="b" type="button">
<input value="n" type="button">
<input value="m" type="button">
<input value="+" type="button">
<input value="." type="button">
<input value="-" type="button">
<input disabled="disabled" value=" " type="button">
</div><div>
<input id="Button1" value="MAG." type="button" onclick="switchVisible();">
<input value=" " type="button">
<input id="Button1" value="MAG." type="button" onclick="switchVisible();">
</div></div>
<div id="Div2" style="display:none" class="keyboard"><div>
<input value="!" type="button">
<input value=""" type="button">
<input value="·" type="button">
<input value="$" type="button">
<input value="%" type="button">
<input value="&" type="button">
<input value="/" type="button">
<input value="(" type="button">
<input value=")" type="button">
<input value="=" type="button">
<input value="Borrar" type="button">
</div><div>
<input value="Q" type="button">
<input value="W" type="button">
<input value="E" type="button">
<input value="R" type="button">
<input value="T" type="button">
<input value="Y" type="button">
<input value="U" type="button">
<input value="I" type="button">
<input value="O" type="button">
<input value="P" type="button">
<input value="^" type="button">
<input value="*" type="button">
</div><div>
<input value="A" type="button">
<input value="S" type="button">
<input value="D" type="button">
<input value="F" type="button">
<input value="G" type="button">
<input value="H" type="button">
<input value="J" type="button">
<input value="K" type="button">
<input value="L" type="button">
<input value="Ñ" type="button">
<input value="¨" type="button">
<input value="Ç" type="button">
</div><div>
<input value=">" type="button">
<input value="Z" type="button">
<input value="X" type="button">
<input value="C" type="button">
<input value="V" type="button">
<input value="B" type="button">
<input value="N" type="button">
<input value="M" type="button">
<input value=";" type="button">
<input value=":" type="button">
<input value="_" type="button">
<input disabled="disalbed" value="" type="button">
</div><div>
<input id="Button1" value="Min." type="button" onclick="switchVisible();">
<input value=" " type="button">
<input id="Button1" value="Min." type="button" onclick="switchVisible();">
</div></div></div></div>
<div>
<label>Track Search</label> - <input id="text" type="text" readonly="readonly">
</div>
<script type="text/javascript">
function switchVisible() {
var div1=document.getElementById('Div1');
var div2=document.getElementById('Div2');
if (div1 !== undefined && div2 !== undefined) {
div1.style.display = div2.style.display === '' ? 'none' : div2.style.display === 'none' ? 'none' : 'block';
div2.style.display = div1.style.display === 'block' ? 'none' : 'block';
}
}
</script>
</body>
</html>
There are a few issues that need to be addressed:
Major issues:
Console JS error - there is no button with an ID of "clear".
I didn't see a button with an ID of "back"
I'm guessing it's the "Borrar" button, but it lacks an ID.
It would also need to be skipped by the loop in the init function discussed in the next point.
There are 4 <input id="Button1"...:
IDs need to be unique.
But these buttons do need a class or id to prevent the makeClickHandler from attaching an onclick function and overriding the inline onclick defintiion.
/* find all the the input type="button" elements */
if(i[c].type==='button' && (i[c].id !== "Button1" || i[c].id !== "back")) {
/* add an onclick handler to each of them and set the function to call */
i[c].addEventListener('onclick',makeClickHandler(c));
}
Minor issues:
Move the IIFE script in the <head> to the bottom of the page; then you won't need to add an event listener for "onload".
The code is almost unreadable. Please use indention properly and be consistent!
There's an input with a misspelled disable - disabled="disalbed"
By convention, element id's shouldn't start with a capital letter.
Avoid using onclick or any inline javascript. This is called a separation of concerns.
Brush up/learn about event delegation; it'll make the code cleaner.
I have written a calculator script which currently allows me to type invalid input values like 5*****5. Such inputs (where one arithmetic operator like *, + etc immediately follows another) should be restricted because they make no sense. How can I modify my code to restrict such inputs?
function c(val) {
var1 = $("#bar").val(val);
}
function v(val) {
var2 = $("#bar").val($("#bar").val() + val);
}
function equal() {
var3 = c(eval($("#bar").val()));
}
function reset() {
var4 = $("#bar").val("");
}
$(document).ready(function() {
$("#backspace").click(function() {
var barValue = $("#bar").val();
$("#bar").val(barValue.substring(0, barValue.length - 1));
});
});
<p>
<input type="text" id="bar" size="15" readonly>
<input type="button" value="C" onclick="reset('')">
</p>
<p>
<input type="button" value="←" id="backspace">
<input type="button" value="" onclick="">
<input type="button" value="" onclick="">
<input type="button" value="" onclick="">
<input type="button" value="" onclick="">
</p>
<p>
<input type="button" value="7" onclick="v('7')">
<input type="button" value="8" onclick="v('8')">
<input type="button" value="9" onclick="v('9')">
<input type="button" value="/" onclick="v('/')">
<input type="button" value="" onclick="">
</p>
<p>
<input type="button" value="4" onclick="v('4')">
<input type="button" value="5" onclick="v('5')">
<input type="button" value="6" onclick="v('6')">
<input type="button" value="*" onclick="v('*')">
<input type="button" value="" onclick="">
</p>
<p>
<input type="button" value="1" onclick="v('1')">
<input type="button" value="2" onclick="v('2')">
<input type="button" value="3" onclick="v('3')">
<input type="button" value="-" onclick="v('-')">
<input type="button" value="" onclick="">
</p>
<p>
<input type="button" value="0" onclick="v('0')">
<input type="button" value="." onclick="v('.')">
<input type="button" value="+" onclick="v('+')">
<input type="button" value="=" onclick="equal()" id="equal">
<input type="button" value="" onclick="">
</p>
<div id="history"></div>
Here is a JSFiddle Link to the full source.
Use regular expressions. Test to see if last value is +,-,*,or /
If the lastChar matches this criteria and so does the passed value do not do anything.
function v(val) {
var patt = /\+|\-|\*|\//
var barValue = $("#bar").val();
var lastChar = barValue.substring(barValue.length, barValue.length - 1);
if (patt.test(lastChar) && patt.test(val)) {
//do nothing as current val and lastChar are mathematical characters
} else {
//update the formula
var2 = $("#bar").val($("#bar").val() + val);
}
}
I have this HTML (is just a simple pocket calculator):
<html>
<head>
<script type="text/javascript" src="js/SimpleCalculator.js"></script>
</head>
<body>
<h2>Simple Calculator</h2>
<div class="calculator">
<div class="display"><input type="text" readonly size="20" id="dsp"></div>
<div class="keys">
<p><input type="button" value="7" onclick='getValue(this.value)'>
<input type="button" value="8" onclick='getValue(this.value)'>
<input type="button" value="9" onclick='getValue(this.value)'>
<input type="button" value="/" onclick='getValue(this.value)'>
</p>
<p><input type="button" value="4" onclick='getValue(this.value)'>
<input type="button" value="5" onclick='getValue(this.value)'>
<input type="button" value="6" onclick='getValue(this.value)'>
<input type="button" value="*" onclick='getValue(this.value)'>
</p>
<p><input type="button" value="1" onclick='getValue(this.value)'>
<input type="button" value="2" onclick='getValue(this.value)'>
<input type="button" value="3" onclick='getValue(this.value)'>
<input type="button" value="-" onclick='getValue(this.value)'>
</p>
<p><input type="button" value="0" onclick='getValue(this.value)'>
<input type="button" value="." onclick='getValue(this.value)'>
<input type="button" value="+" onclick='getValue(this.value)'></p>
<p><input type="button" value="C" onclick='getValue(this.value)'>
<input type="button" value="=" onclick='getValue(this.value)'></p>
</div>
</div>
</body>
</html>
and the JS file:
var s = '';
function getValue(val){
alert(val);
if (val != 'C' && val != '='){s += val;
document.getElementById("dsp").value+=val;}
if (val === 'C')
document.getElementById("dsp").value = " ";
if (val === '='){
alert(document.getElementByVal("dsp").value);
var res = eval(s);
document.getElementByVal("dsp").value = res;
}
}
The keys are displayed (numbers and math signs), alerts work fine but the evaluation of the expession is not displayed. Where am I wrong ?
You should use getElementById not ByVal, which is not a function.
var s = '';
function getValue(val){
if (val != 'C' && val != '='){s += val;
document.getElementById("dsp").value+=val;}
if (val === 'C')
document.getElementById("dsp").value = " ";
if (val === '='){
alert(document.getElementById("dsp").value);
var res = eval(s);
document.getElementById("dsp").value = res;
}
}
<h2>Simple Calculator</h2>
<div class="calculator">
<div class="display"><input type="text" readonly size="20" id="dsp"></div>
<div class="keys">
<p><input type="button" value="7" onclick='getValue(this.value)'>
<input type="button" value="8" onclick='getValue(this.value)'>
<input type="button" value="9" onclick='getValue(this.value)'>
<input type="button" value="/" onclick='getValue(this.value)'>
</p>
<p><input type="button" value="4" onclick='getValue(this.value)'>
<input type="button" value="5" onclick='getValue(this.value)'>
<input type="button" value="6" onclick='getValue(this.value)'>
<input type="button" value="*" onclick='getValue(this.value)'>
</p>
<p><input type="button" value="1" onclick='getValue(this.value)'>
<input type="button" value="2" onclick='getValue(this.value)'>
<input type="button" value="3" onclick='getValue(this.value)'>
<input type="button" value="-" onclick='getValue(this.value)'>
</p>
<p><input type="button" value="0" onclick='getValue(this.value)'>
<input type="button" value="." onclick='getValue(this.value)'>
<input type="button" value="+" onclick='getValue(this.value)'></p>
<p><input type="button" value="C" onclick='getValue(this.value)'>
<input type="button" value="=" onclick='getValue(this.value)'></p>
</div>
</div>
Change the last line to use getElementById, not getElementByVal