JavaScript: Why do we use arguments object in a function? [duplicate]

Question

I noticed that in some functions the arguments object is used:

function fn(arg1, arg2)
{
    console.log(arguments[0])
}

fn(1, 2); // 1

Why it is useful?

The arguments object is kind of special, but it's most commonly used for a variable number of args. There are useful properties like caller and callee as well. More info: developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/… — Brennan
– Brennan, Commented Jan 21, 2015 at 6:01

JLRishe · Accepted Answer · 2015-01-21 06:59:55Z

2

In your example, it's not useful and not a good idea. It can be useful when you want a function that can accept an indefinite number of arguments:

function sum() {
    var total = 0;
    for (var i = 0; i < arguments.length; i += 1) {
        total += arguments[i];
    }
    return total;
}

console.log(sum(5, 6, 7, 8));   // 26

Note that ES6 allows the use of rest parameters which would be more useful in most cases where arguments are used nowadays:

function sum(...values) {
    return values.reduce(function (prev, cur) {
        return prev + cur;
    }, 0);
}

edited Jan 21, 2015 at 6:59

answered Jan 21, 2015 at 6:00

JLRishe

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