javascript - 构建数组监听器

Question

有没有办法将监听器附加到另一个进程正在构建的数组，以便当 array.length 达到特定值时，监听器执行回调并触发适当的代码？

fooArray = [];
// another code adds objects to array

if (fooArray.length = 5) {
  // callback
} else {
  // continue checking fooArray.length
}

Answer 1

你必须使用自己的方法来改变数组

Array.prototype.myPush = function () {

    this.push.apply( this, arguments );
    if ( this._binder && this._binder.test.call( this ) ) {
        this._binder.callback.call( this );
    }

}

Array.prototype.bind = function (tester, callback) {
    this._binder = {
        test: tester,
        callback: callback
    };
}

var arr = [4, 6, 9, 20];
arr.bind( function () {
    return this.length >= 5;
}, function () {
    console.log( "Array has exceeded" );
} );

arr.myPush( 40 );