javascript - get value parameter from input text - javascript

I want to get the value of a text input. I would like to do this by using id and getElementById :
here HTML code :
<form>
<fieldset>
<legend>Input ordinate :</legend>
<input type="text" id="ordinateId" name="input"/>
<input type="button" id="startbuttonId" value="Start particle"/>
</fieldset>
</form>
and Javascript :
<script type="text/javascript">
var button = document.getElementById("startbuttonId");
var value = document.getElementById("ordinateId").value;
console.log(value);
button.onclick = function() {
console.log(value);
}
</script>
but into the console, nothing appears for value. Where is the problem ?
Thanks

The problem is that you are checking for the input's value before it is set(on document load). Just move the variable declaration within the click function like so:
var button = document.getElementById("startbuttonId");
button.onclick = function() {
var value = document.getElementById("ordinateId").value;
console.log(value);
}
JSFiddle

You need to get the value again when the event fires. Just move your var value
button.onclick = function() {
var value = document.getElementById("ordinateId").value;
console.log(value);
}

With your current script you are assigning value only once, which I am assuming is an empty string. You need to put the assignment inside the function so it gets the current value of the input when it is clicked.
<script type="text/javascript">
var button = document.getElementById("startbuttonId");
button.onclick = function() {
var value = document.getElementById("ordinateId").value;
console.log(value);
}
</script>

Related

I'm trying to save the content of an input into local storage when a button is clicked. What am I doing wrong?

so I have an input element with the id of "answer" and a button. I've added an event listener for the button and tried to call a function that saves the text inside of the input into local storage. The console is telling me that "innerHTML" is null, but i'm not sure what I'm supposed to do.
<input type="text" id="answer" />
<button id="button">click me</button>
var inputAnswer = document.getElementById("#answer")
var buttonEl = document.getElementById("button")
buttonEl.addEventListener("click", saveToStorage())
function saveToStorage() {
localStorage.setItem("task", inputAnswer.innerHTML);
}
<input type="text" id="answer" />
<button id="button">click me</button>
<script type="text/javascript">
var inputAnswer = document.getElementById("answer");
var buttonEl = document.getElementById("button");
buttonEl.addEventListener("click", addAnswerToLocalStorage);
function addAnswerToLocalStorage() {
const value = inputAnswer.value;
localStorage.setItem("answer", value);
}
</script>
There is mistake in getting the reference of input field. Instead of #answer document.getElementById("#answer") it should be only answer only. Further, I checked it on my local machine and it is working fine.
getElementById() expects an ID, no hashtag. Change var inputAnswer = document.getElementById("#answer") to var inputAnswer = document.getElementById("answer") (remove the #).
buttonEl.addEventListener("click", saveToStorage()) invokes the saveToStorage() function immediately, which is not what you want. Instead, pass it as a reference: buttonEl.addEventListener("click", saveToStorage).

How can I display the input value?

I would like to show what I write in the input, but everytime I try the alert window shows "undefined".
This is the code.
Thanks.
<body>
<input id="input"></input>
<button id="search">search</button>
<script>
document.getElementById('search').addEventListener("click", show);
var input = getElementById('input');
var search = input.value;
function show() {
alert(search);
}
</script>
</body>
First you need to use document.getElementById instead of just getElementById.
Then you need to put var search = input.value inside the show function so that it gets the current value each time you want to show it, and not just the initial one.
document.getElementById('search').addEventListener("click", show);
var input = document.getElementById('input');
function show() {
var search = input.value;
alert(search);
}
<input id="input"></input>
<button id="search">search</button>
you must bring var search into show function declaration in order to get new value of search box every time the event occurs.
function show(){
var search = input.value;
alert(search);
}

Simple two button counter html jquery javascript

I am new to Jquery and Javascript. I've only done the intros for codeacademy and I have what I remembered from my python days.
I saw this tutorial:
http://www.codecademy.com/courses/a-simple-counter/0/1
I completed the tutorial and thought: "I should learn how to do this with Jquery".
So I've been trying to use what I understand to do so. My issue is that I don't know how to pass an argument for a variable from HTML to Jquery(javascript).
Here is my code:
HTML
<body>
<label for="qty">Quantity</label>
<input id="qty" type = "number" value = 0 />
<button class = "botton">-1</button>
<button class = "botton">+1</button>
<script type="text/javascript" src="jquery-1.11.1.min.js"></script>
<script type="text/javascript" src="test.js"></script>
</body>
Jquery/Javascript:
//create a function that adds or subtracts based on the button pressed
function modify_qty(x) {
//on click add or subtract
$('.botton').click(function(){
//get the value of input field id-'qty'
var qty = $('#qty').val();
var new_qty = qty + x;
//i don't want to go below 0
if (new_qty < 0) {
new_qty = 0;
}
//put new value into input box id-'qty'
$('#qty').html(new_qty)
})
};
$(document).ready(modify_qty);
How do I pass an argument of 1 or -1 to the function? I was using onClick() but that seemed redundant because of the $('.botton').click(function(){}).
Thank you
If you use data attributes on your buttons you can get the value you want.
HTML:
<button class = "botton" data-value="-1">-1</button>
<button class = "botton" data-value="1">+1</button>
JS:
function modify_qty() {
//on click add or subtract
$('.botton').click(function(){
//get the value of input field id-'qty'
var qty = parseInt($('#qty').val());
var new_qty = qty + parseInt($(this).data('value'));
//i don't want to go below 0
if (new_qty < 0) {
new_qty = 0;
}
//put new value into input box id-'qty'
$('#qty').val(new_qty)
})
};
$(document).ready(modify_qty);
More compact JS:
$(function() {
//on click add or subtract
$('.botton').click(function(){
//get the value of input field id-'qty'
var $qty = $('#qty'),
currentValue = parseInt($qty.val());
$qty.val(Math.max(0, currentValue + parseInt($(this).data('value'))));
})
});
Update:
Realized you could do this without the data attributes if want to since your button text is the same as your value.
$(function() {
//on click add or subtract
$('.botton').click(function(){
//get the value of input field id-'qty'
var $qty = $('#qty'),
currentValue = parseInt($qty.val()),
newValue = currentValue + parseInt($(this).text());
$qty.val(Math.max(0, newValue));
})
});
Here's a fiddle to help you grasp the what's going on. Basically, the reference to the element that triggered the event is $(this) or event.target. Things get a bit more complicated with self refence depending on the context you are in, however for $('selector').on('event',function(event){ console.log($(this)) //is the reference to $('selector') });. .attr() -> list of the element's attributes.

pass a variable name and evaluate it to that variable's value

I have a form with many buttons all of which print a value in the relevant textbox. the problem is the value is a fairly long text string and I would like to create a shorter variable eg. 'text' and make that variable equal to eg. 'some long sentence that I only want to type once'. any idea how I can edit this code to make this possible
function setInput(button, setValue) {
var buttonVal = button.value,
textbox = document.getElementById('input_' + buttonVal);
textbox.value = setValue;
<html>
<input type='submit' name='submit_a' value="a"
onclick="setInput(this,'make_me_a_variable'); return false;">
</html>
var textLookup = {
btnName1: "Long text",
btnName2: "Longer text"
};
// inside your function
var buttonText = ...,
inputText = textLookup[buttonText];
// do stuff with inputText;
Instead of defining the event handler in the HTML code, you could also create the event handler with javascript. You need to do that in another event handler for document.onload. When you do it earlier, the input HTML element might not have been parsed and created yet, so no event handler for it can be added.
<script>
// store your text in a variable
var inputText = 'make_me_a_variable';
// define some code which is executed when the page is loaded:
document.addEventListener("load",function(event){
// get the input by the id property I added to the HTML below.
var input = document.getElementById('submit_a');
// add an event handler for the click event (replaces the onclick HTML property)
input.addEventListener("click",function(event) {
setInput(this, inputText);
return false;
});
});
</script>
[...]
<input id="submit_a" type='submit' name='submit_a' value="a" >
You can create a variable and assign your long text to the variable and use it where ever you want.
Modified code
var longText = 'long text here'.
function setInput(button) {
var buttonVal = button.value,
textbox = document.getElementById('input_' + buttonVal);
textbox.value = longText ;
}
Html:
<input type='submit' name='submit_a' value="a"
onclick="setInput(this); return false;">

Add form input to array with javascript using unshift()

I am trying to add elements to an array via a form. I am using the unshift() method. The code below doesn't work and I would like to know why.
<form>
<input id="input"> </input>
<input type = "button" id="button"> Click me </input>
</form>
<script>
var input = document.getElementById("input").value;
var button = document.getElementById("button");
var myArray = [];
myArray.unshift(input);
button.onclick = function alerted (){
alert(myArray);
};
</script>
Your quoted code runs immediately when the page is loaded. The form field won't have anything in it then, so its value will be ''. When you alert that, the default toString operation on the array will result in '' and the alert will be blank.
You want to run your unshift code in response to a user event, such as the button being clicked, rather than right away. You can do that by setting input to be the element (remove .value from that line) and then moving your line with unshift into the function you're assigning to onclick, adding the .value there:
button.onclick = function alerted (){
myArray.unshift(input.value);
alert(myArray);
};
Other notes:
You never write </input>. Normally you don't close input tags at all. If you're writing XHTML (you probably aren't), you'd put the / within the main input tag like this: <input id="input" />. But again, you're probably not writing XHTML, just HTML.
The value (caption) of an input button goes in its value attribute, not content within opening and closing tags. (You would use opening and closing tags with the button element, not input.)
Taking all of that together, here's a minimalist update: Live copy | source
<form>
<input id="input"><!-- No ending tag -->
<input type = "button" id="button" value="Click me"><!-- No ending tag, move value where it should be -->
</form>
<script>
var input = document.getElementById("input"); // No .value here
var button = document.getElementById("button");
var myArray = [];
button.onclick = function alerted (){
myArray.unshift(input.value); // Moved this line, added the .value
alert(myArray);
};
</script>
DEMO
You need to a) get the value in the click and b) return false if you want the button to not submit. I changed to button. Alternative is <input type="button" value="click me" id="button" />
You may even want to empty and focus the field on click...
<form>
<input id="input" type="text"/>
<button id="button"> Click me </button>
</form>
<script>
var input = document.getElementById("input"); // save the object
var button = document.getElementById("button");
var myArray = [];
button.onclick = function alerted (){
myArray.unshift(input.value); // get the value
alert(myArray);
return false;
};
</script>​
You're not getting the new value in the onclick function.
Try this: http://jsfiddle.net/SeqWN/4/
var button = document.getElementById("button");
var i = document.getElementById("input");
var myArray = [];
button.onclick = function alerted (){
myArray.unshift(i.value);
alert(myArray);
};​

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