What is the difference between call and apply?

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太阳男子 2020-11-21 07:12

What is the difference between using call and apply to invoke a function?

var func = function() {
  alert(\'hello!\');
};

24条回答

一向 (楼主)

2020-11-21 07:55

From the MDN docs on Function.prototype.apply() :

The apply() method calls a function with a given this value and arguments provided as an array (or an array-like object).

Syntax
fun.apply(thisArg, [argsArray])

From the MDN docs on Function.prototype.call() :

The call() method calls a function with a given this value and arguments provided individually.

Syntax
fun.call(thisArg[, arg1[, arg2[, ...]]])

From Function.apply and Function.call in JavaScript :

The apply() method is identical to call(), except apply() requires an array as the second parameter. The array represents the arguments for the target method.

Code example :

var doSomething = function() {
    var arr = [];
    for(i in arguments) {
        if(typeof this[arguments[i]] !== 'undefined') {
            arr.push(this[arguments[i]]);
        }
    }
    return arr;
}

var output = function(position, obj) {
    document.body.innerHTML += 'output ' + position + '
' + JSON.stringify(obj) + '\n
\n
';
}

output(1, doSomething(
    'one',
    'two',
    'two',
    'one'
));

output(2, doSomething.apply({one : 'Steven', two : 'Jane'}, [
    'one',
    'two',
    'two',
    'one'
]));

output(3, doSomething.call({one : 'Steven', two : 'Jane'},
    'one',
    'two',
    'two',
    'one'
));