Can a JavaScript function take unlimited arguments? Something like this:
testArray(1, 2, 3, 4, 5...);
I am trying:
var arr = [];
function testArray(A) {
arr.push(A);
}
But this doesn't work (output is only the first argument). Or the only way is:
function testArray(a, b, c, d, e...) {
}
Thanks
There's a weird "magic" variable you can reference called "arguments":
function manyArgs() {
for (var i = 0; i < arguments.length; ++i)
alert(arguments[i]);
}
It's like an array, but it's not an array. In fact it's so weird that you really shouldn't use it much at all. A common practice is to get the values of it into a real array:
function foo() {
var args = Array.prototype.slice.call(arguments, 0);
// ...
In that example, "args" would be a normal array, without any of the weirdness. There are all sorts of nasty problems with "arguments", and in ECMAScript 5 its functionality will be curtailed.
edit — though using the .slice() function sure is convenient, it turns out that passing the arguments object out of a function causes headaches for optimization, so much so that functions that do it may not get optimized at all. The simple, straightforward way to turn arguments into an array is therefore
function foo() {
var args = [];
for (var i = 0; i < arguments.length; ++i) args[i] = arguments[i];
// ...
}
As of ECMAScript 2015 (or ES6) we also have access to rest parameters that give us a slightly cleaner way to manage arguments:
function foo(a, b, ...others) {
console.log("a and b are ", a, b);
for (let val of others) {
console.log(val);
}
}
foo(1, 2, 3, 4, 5);
At the time of this writing, this is supported by Chrome 47+, Firefox 15+, and Edge. The feature is also available via both Babel and TypeScript transpiling down to ES5.
With ECMAScript 6, you can use rest of arguments syntax:
const testArray = (...args) => {
console.log(args);
};
testArray(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
Javascript ES5
function testArray(){
for(index = 0; index < arguments.length; i++) {
alert(arguments[index])
}
}
Javascript ES6
const testArray = (...arg) => console.log(arg)
There are some legacy methods but I prefer the ES6 and newer versions, So if I wanna implement this, I wrote it like below:
const func = (...arg) => console.log(arg);
Simple and cutting edge of tech.
var arr = [];
function testArray() {
Array.prototype.push.apply(arr, arguments);
}
function toArray() {
return arguments;
}
var myargs = toArray(1, 2, 3, 4, 5, 6);
The arguments keyword is available in every js function
arguments is not of "type" Array, its just a sort of "iterable", and that is pretty lame on JS side.You can also just "cast" it, saving you the ugly loop:
var getArguments = function() {
return arguments;
};
var foo = getArguments(1,2,3,4);
// console.log(foo.slice()); => TypeError: foo.slice is not a function
var foo = Object.values(foo);
console.log(foo); // => [ 1, 2, 3, 4 ]
foo.push(5);
console.log(foo); // => [ 1, 2, 3, 4, 5 ]
const outputDiv=document.querySelector('.output');
const output=(...x)=>{
return outputDiv.innerHTML=x;
}
output(1,2,3,4,['hello',5,6],true,null);<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Javascript Practice</title>
<link href="https://fonts.googleapis.com/css2?family=Raleway:ital,wght@0,100;0,200;0,300;0,400;0,500;0,600;0,700;0,800;0,900;1,100;1,200;1,300;1,400;1,500;1,600;1,800;1,900&display=swap" rel="stylesheet">
<style>
body{font-family: 'Raleway', sans-serif; background-color: #060606;}
.center{height:100vh; width: 100%; display: grid;align-items:center;justify-content: center;}
.output{font-size: 15px;color: rgb(59, 59, 255);font-weight: 200;}
</style>
</head>
<body>
<div class="center">
<div class='output'></div>
</div>
<script src="js.js"></script>
</body>
</html>
...([one_arg])...