How do I square a number's digits? e.g.:
square(21){};
should result in 41 instead of 441
This is easily done with simple math. No need for the overhead of string processing.
var result = [];
var n = 21;
while (n > 0) {
result.push(n%10 * n%10);
n = Math.floor(n/10);
}
document.body.textContent = result.reverse().join("");
In a loop, while your number is greater than 0, it...
gets the remainder of dividing the number by 10 using the % operator
squares it and adds it to an array.
reduces the original number by dividing it by 10, dropping truncating to the right of the decimal, and reassigning it.
Then at the end it reverses and joins the array into the result string (which you can convert to a number if you wish)
I think he means something like the following:
var output = "";
for(int i = 0; i<num.length; i++)
{
output.concat(Math.pow(num[i],2).toString());
}
I believe this is what the OP is looking for? The square of each digit?
var number = 12354987,
var temp = 0;
for (var i = 0, len = sNumber.length; i < len; i += 1) {
temp = String(number).charAt(i);
output.push(Number(temp) * Number(temp));
}
console.log(output);
Split the string into an array, return a map of the square of the element, and rejoin the resulting array back into a string.
function squareEachDigit(str) {
return str.split('').map(function (el) {
return (+el * +el);
}).join('');
}
squareEachDigit('99') // 8181
squareEachDigit('52') // 254
DEMO
function sq(n){
var nos = (n + '').split('');
var res="";
for(i in nos){
res+= parseInt(nos[i]) * parseInt(nos[i]);
}
return parseInt(res);
}
var result = sq(21);
alert(result)
You'll want to split the numbers into their place values, then square them, then concatenate them back together. Here's how I would do it:
function fn(num){
var strArr = num.toString().split('');
var result = '';
for(var i = 0; i < strArr.length; i++){
result += Math.pow(strArr[i], 2) + '';
}
return +result;
}
Use Math.pow to square numbers like this:
Math.pow(11,2); // returns 121
I want to try and sum up distinct value from a list.. currently i am able to do so if theres only 2 similar record. If theres more than 2 i am not able to do the checking. Following is the javascript code:
function validateData(){
var total = document.frm.size.value;
var msg="";
var tbxA;
var tbxB;
var tbxA2;
var tbxB2;
var tbxC;
var totalValue =0;
var repeatedValue= 0;
var row = 0;
var row2 = 0;
for(var i=0; i<parseInt(total); i++){
tbxA = document.getElementById('tbx_A'+i).value;
tbxB = document.getElementById('tbx_B'+i).value-0;
tbxC = document.getElementById('tbx_C'+i).value;
for(var j=i+1; j<parseInt(total); j++){
tbxA2 = document.getElementById('tbx_A'+j).value;
tbxB2 = document.getElementById('tbx_B'+j).value-0;
if (tbxA==tbxA2) {
totalValue = tbxB + tbxB2;
}
if (totalValue != tbxC) {
repeatedValue= 1;
row = i;
row2 = j;
msg+="*total value does not add up at row " +(row2+1);
break;
}
}
if(repeatedValue== 1){
break;
}
}
return msg;
}
For example A:type of fruit, B: total of each fruit, C: how many bought at a time
total of C should be equal to B. i.e Apple: 3+3+4 = 10. So if the total is not equals to 10 it should prompt me an error.
A B C
Apple 10 3
Orange 10 10
Apple - 3
Apple - 4
My code above will prompt error bt it doesnt go beyond 2nd occurence of Apple.
So yes, how should i go about to ensure it loop through the whole list to sum up all similar values?
Thanks in advance for any possible help!
Try this:
var total = +document.frm.size.value,
data = {};
for(var i=0; i<total; ++i) {
var key = document.getElementById('tbx_A'+i).value;
data[key] = data[key] || {B:0, C:0};
data[key].B += +document.getElementById('tbx_B'+i).value || 0;
data[key].C += +document.getElementById('tbx_C'+i).value || 0;
}
for(var i in data) {
if(data.hasOwnProperty(i) && data[i].B != data[i].C) {
return "total value does not add up";
}
}
return "";
Some comments:
parseInt (and parseFloat) is very slow. + operator before string converts it to a number much faster. But if you really want to make sure the numbers are integers, use Math.floor(), Math.round(), Math.ceil() or the faster but illegible |0.
In case you really want parseInt (e.g. you want to convert '123foobar' into 123), always use a radix. For example: parseInt('123', 10)
Avoid doing calculations at the condition of a loop, because they run at each iteration. Just do the calculation once before the loop and save the result in a variable.
function function1() {
arr = document.getElementById("textfield").value;
arr = arr.split(",");
length = arr.length;
largestNum = -9999;
for (i = 0; i < length; i++) {
if (arr[i] > largestNum) {
largestNum = arr[i];
}
}
alert("Largest number: " + largestNum);
}
can someone tell me what the hell is going on here, i have no idea why it's giving me 8 instead of 12
http://jsfiddle.net/qkLpA/15/
edit - fixed here: http://jsfiddle.net/qkLpA/12/
You're splitting a string, so each element of the resulting array will be a string. When you compare strings, it goes character-by-character, and 8 is larger than 1, so it never goes on to the 2.
The solution is to convert the items into numbers after splitting it:
arr = arr.split(",").map(function(s) { return parseInt(s, 10); });
If the map is confusing, you could also be less fancy and just use a for loop to convert them:
arr = arr.split(",");
for(var i = 0; i < arr.length; i++) {
arr[i] = parseInt(arr[i], 10);
}
You may also want to consider using -Infinity as the initial largestNum rather than -9999.
There's a much shorter way to get the largest humber:
function function1() {
var arr = document.getElementById("textfield").value;
arr = arr.split(",");
var max = Math.max.apply(null, arr);
alert("Largest number: " + max);
}
Fiddle
Your problem is that the .split() of the textfield string, creates an array of strings and not numbers. As a consequence, your comparison if (arr[i] > largestNum) in the for loop, is in reality a lexicographical comparison of strings, instead of a numerical comparison of integers, as you might have thought. That is why the "8" is larger than the "12".
You can confirm this in the updated jsfiddle which converts the strings to integers before comparing.
Hi I am trying to sum an array on Javascript with the following codes.
var data[]:
var total=0;
data.push[x]; // x is numbers which are produced dynamically.
for(var i=0, n=data.length; i < n; i++)
{
total=total+data[i];
}
alert(total)
for example if x values are are respectively 5,11,16,7. It shows the total value as 511167 not sum the values 5+11+16+7=39
Do you have any idea why it results like that?
Thanks.
Use parseInt() function javascript
total=parseInt(total)+parseInt(data[i]);
Try with parseInt:
total=total+parseInt(data[i]);
Simply whip a unary + before data[i] to convert the string values to numeric values:
total = total + (+data[i]);
Even better, use += instead of total=total+...:
total += +data[i];
JSFiddle demo.
Try this one:
var total = 0;
for (var i = 0; i < someArray.length; i++) {
total += someArray[i] << 0;
}
Use parseInt() javascript function....
total = total + parseInt(data[i]);
This looks the 'x' which you mention come dynamically has a string type. Just check the "typeof x".
What's the shortest way (within reason) to generate a random alpha-numeric (uppercase, lowercase, and numbers) string in JavaScript to use as a probably-unique identifier?
I just came across this as a really nice and elegant solution:
Math.random().toString(36).slice(2)
Notes on this implementation:
This will produce a string anywhere between zero and 12 characters long, usually 11 characters, due to the fact that floating point stringification removes trailing zeros.
It won't generate capital letters, only lower-case and numbers.
Because the randomness comes from Math.random(), the output may be predictable and therefore not necessarily unique.
Even assuming an ideal implementation, the output has at most 52 bits of entropy, which means you can expect a duplicate after around 70M strings generated.
If you only want to allow specific characters, you could also do it like this:
function randomString(length, chars) {
var result = '';
for (var i = length; i > 0; --i) result += chars[Math.floor(Math.random() * chars.length)];
return result;
}
var rString = randomString(32, '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ');
Here's a jsfiddle to demonstrate: http://jsfiddle.net/wSQBx/
Another way to do it could be to use a special string that tells the function what types of characters to use. You could do that like this:
function randomString(length, chars) {
var mask = '';
if (chars.indexOf('a') > -1) mask += 'abcdefghijklmnopqrstuvwxyz';
if (chars.indexOf('A') > -1) mask += 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
if (chars.indexOf('#') > -1) mask += '0123456789';
if (chars.indexOf('!') > -1) mask += '~`!##$%^&*()_+-={}[]:";\'<>?,./|\\';
var result = '';
for (var i = length; i > 0; --i) result += mask[Math.floor(Math.random() * mask.length)];
return result;
}
console.log(randomString(16, 'aA'));
console.log(randomString(32, '#aA'));
console.log(randomString(64, '#A!'));
Fiddle: http://jsfiddle.net/wSQBx/2/
Alternatively, to use the base36 method as described below you could do something like this:
function randomString(length) {
return Math.round((Math.pow(36, length + 1) - Math.random() * Math.pow(36, length))).toString(36).slice(1);
}
UPDATED:
One-liner solution, for random 20 characters (alphanumeric lowercase):
Array.from(Array(20), () => Math.floor(Math.random() * 36).toString(36)).join('');
Or shorter with lodash:
_.times(20, () => _.random(35).toString(36)).join('');
Another variation of answer suggested by JAR.JAR.beans
(Math.random()*1e32).toString(36)
By changing multiplicator 1e32 you can change length of random string.
Or to build upon what Jar Jar suggested, this is what I used on a recent project (to overcome length restrictions):
var randomString = function (len, bits)
{
bits = bits || 36;
var outStr = "", newStr;
while (outStr.length < len)
{
newStr = Math.random().toString(bits).slice(2);
outStr += newStr.slice(0, Math.min(newStr.length, (len - outStr.length)));
}
return outStr.toUpperCase();
};
Use:
randomString(12, 16); // 12 hexadecimal characters
randomString(200); // 200 alphanumeric characters
This is cleaner
Math.random().toString(36).substr(2, length)
Example
Math.random().toString(36).substr(2, 5)
function randomString(len) {
var p = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
return [...Array(len)].reduce(a=>a+p[~~(Math.random()*p.length)],'');
}
Summary:
Create an array of the size we want (because there's no range(len) equivalent in javascript.
For each element in the array: pick a random character from p and add it to a string
Return the generated string.
Some explanation:
[...Array(len)]
Array(len) or new Array(len) creates an array with undefined pointer(s). One-liners are going to be harder to pull off. The Spread syntax conveniently defines the pointers (now they point to undefined objects!).
.reduce(
Reduce the array to, in this case, a single string. The reduce functionality is common in most languages and worth learning.
a=>a+...
We're using an arrow function.
a is the accumulator. In this case it's the end-result string we're going to return when we're done (you know it's a string because the second argument to the reduce function, the initialValue is an empty string: ''). So basically: convert each element in the array with p[~~(Math.random()*p.length)], append the result to the a string and give me a when you're done.
p[...]
p is the string of characters we're selecting from. You can access chars in a string like an index (E.g., "abcdefg"[3] gives us "d")
~~(Math.random()*p.length)
Math.random() returns a floating point between [0, 1) Math.floor(Math.random()*max) is the de facto standard for getting a random integer in javascript. ~ is the bitwise NOT operator in javascript.
~~ is a shorter, arguably sometimes faster, and definitely funner way to say Math.floor( Here's some info
I think the following is the simplest solution which allows for a given length:
Array(myLength).fill(0).map(x => Math.random().toString(36).charAt(2)).join('')
It depends on the arrow function syntax.
for 32 characters:
for(var c = ''; c.length < 32;) c += Math.random().toString(36).substr(2, 1)
Random character:
String.fromCharCode(i); //where is an int
Random int:
Math.floor(Math.random()*100);
Put it all together:
function randomNum(hi){
return Math.floor(Math.random()*hi);
}
function randomChar(){
return String.fromCharCode(randomNum(100));
}
function randomString(length){
var str = "";
for(var i = 0; i < length; ++i){
str += randomChar();
}
return str;
}
var RandomString = randomString(32); //32 length string
Fiddle: http://jsfiddle.net/maniator/QZ9J2/
Using lodash:
function createRandomString(length) {
var chars = "abcdefghijklmnopqrstufwxyzABCDEFGHIJKLMNOPQRSTUFWXYZ1234567890"
var pwd = _.sampleSize(chars, length || 12) // lodash v4: use _.sampleSize
return pwd.join("")
}
document.write(createRandomString(8))
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.min.js"></script>
Random Key Generator
keyLength argument is the character length you want for the key
function keyGen(keyLength) {
var i, key = "", characters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
var charactersLength = characters.length;
for (i = 0; i < keyLength; i++) {
key += characters.substr(Math.floor((Math.random() * charactersLength) + 1), 1);
}
return key;
}
keyGen(12)
"QEt9mYBiTpYD"
var randomString = function(length) {
var str = '';
var chars ='0123456789ABCDEFGHIJKLMNOPQRSTUVWXTZabcdefghiklmnopqrstuvwxyz'.split(
'');
var charsLen = chars.length;
if (!length) {
length = ~~(Math.random() * charsLen);
}
for (var i = 0; i < length; i++) {
str += chars[~~(Math.random() * charsLen)];
}
return str;
};
When I saw this question I thought of when I had to generate UUIDs. I can't take credit for the code, as I am sure I found it here on stackoverflow. If you dont want the dashes in your string then take out the dashes. Here is the function:
function generateUUID() {
var d = new Date().getTime();
var uuid = 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g,function(c) {
var r = (d + Math.random()*16)%16 | 0;
d = Math.floor(d/16);
return (c=='x' ? r : (r&0x7|0x8)).toString(16);
});
return uuid.toUpperCase();
}
Fiddle: http://jsfiddle.net/nlviands/fNPvf/11227/
This function should give a random string in any length.
function randString(length) {
var l = length > 25 ? 25 : length;
var str = Math.random().toString(36).substr(2, l);
if(str.length >= length){
return str;
}
return str.concat(this.randString(length - str.length));
}
I've tested it with the following test that succeeded.
function test(){
for(var x = 0; x < 300000; x++){
if(randString(x).length != x){
throw new Error('invalid result for len ' + x);
}
}
}
The reason i have chosen 25 is since that in practice the length of the string returned from Math.random().toString(36).substr(2, 25) has length 25. This number can be changed as you wish.
This function is recursive and hence calling the function with very large values can result with Maximum call stack size exceeded. From my testing i was able to get string in the length of 300,000 characters.
This function can be converted to a tail recursion by sending the string to the function as a second parameter. I'm not sure if JS uses Tail call optimization
A simple function that takes the length
getRandomToken(len: number): string {
return Math.random().toString(36).substr(2, len);
}
Ff you pass 6 it will generate 6 digit alphanumeric number
Nice and simple, and not limited to a certain number of characters:
let len = 20, str = "";
while(str.length < len) str += Math.random().toString(36).substr(2);
str = str.substr(0, len);
One could just use lodash uniqueId:
_.uniqueId([prefix=''])
Generates a unique ID. If prefix is given, the ID is appended to it.
Here's a simple code to generate random string alphabet.
Have a look how this code works.
go(lenthOfStringToPrint); - Use this function to generate the final string.
var letters = {
1: ["q","w","e","r","t","y","u","i","o","p","a","s","d","f","g","h","j","k","l","z","x","c","v","b","n","m"],
2: ["Q","W","E","R","T","Y","U","I","O","P","A","S","D","F","G","H","J","K","L","Z","X","C","V","B","N","M"]
},i,letter,final="";
random = (max,min) => {
return Math.floor(Math.random()*(max-min+1)+min);
}
function go(length) {
final="",letter="";
for (i=1; i<=length; i++){
letter = letters[random(0,3)][random(0,25)];
final+=letter;
}
return final;
}
I used #Nimphious excellent second approach and found that occasionally the string returned was numeric - not alphanumeric.
The solution I used was to test using !isNaN and use recursion to call the function again.
Why bother? I was using this function to create object keys, if all the keys are alphanumeric everything sorts properly but if you use
numbers as keys mixed with alphanumeric (strings) looping through the object will produce a different order to original order.
function newRandomString(length, chars) {
var mask = '';
if (chars.indexOf('a') > -1) mask += 'abcdefghijklmnopqrstuvwxyz';
if (chars.indexOf('A') > -1) mask += 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
if (chars.indexOf('#') > -1) mask += '0123456789';
if (chars.indexOf('$') > -1) mask += '0123456789';
var result = '';
for (var i = length; i > 0; --i) result += mask[Math.floor(Math.random() *
mask.length)];
/*
we need a string not a number !isNaN(result)) will return true if '1234' or '3E77'
because if we're looping through object keys (created by newRandomString()) and
a number is used and all the other keys are strings then the number will
be first even if it was the 2nd or third key in object
*/
//use recursion to try again
if(!isNaN(result)){
console.log('found a number....:'+result);
return newRandomString(length, chars)
}else{
return result;
}
};
var i=0;
while (i < 1000) {
var a = newRandomString(4, '#$aA');
console.log(i+' - '+a);
//now we're using recursion this won't occur
if(!isNaN(a)){
console.log('=============='+i+' - '+a);
}
i++;
}
console.log('3E77:'+!isNaN('3E77'));//true
console.log('1234:'+!isNaN('1234'));//true
console.log('ab34:'+!isNaN('ab34'));//false
After looking at solutions in answers to this question and other sources, this is the solution that is simplest while allowing for modification of the included characters and selection in the length of the returned result.
// generate random string of n characters
function randomString(length) {
const characters = '0123456789abcdefghijklmnopqrstuvwxyz'; // characters used in string
let result = ''; // initialize the result variable passed out of the function
for (let i = length; i > 0; i--) {
result += characters[Math.floor(Math.random() * characters.length)];
}
return result;
}
console.log(randomString(6));
Use md5 library: https://github.com/blueimp/JavaScript-MD5
The shortest way:
md5(Math.random())
If you want to limit the size to 5:
md5(Math.random()).substr(0, 5)