循环中执行setTimeout代码

方法一:

(function () {
    var arr = [100, 200, 300, 400, 500];
    for (var i = 0; i < arr.length; i++) {
        (function (i) {
            setTimeout(function () {
                console.log(i + "----------" + i * Math.random());
            }, arr[i] * Math.random());
        })(i);
    }
}());

方法二:
var arr = [100, 200, 300, 400, 500];
(function (i, len, count, callback) {
    for (; i < len; ++i) {
        (function (i) {
            callback(arr[i]);
        }(i));
    }
}(0, arr.length, 0, function (param) {
    setTimeout(function () {
        console.log(param + "----------" + param * Math.random());
    }, param);
}));

方法三:
var arr = [100, 200, 300, 400, 500];
(function next(i, len, callback) {
    if (i < len) {
        callback(arr[i]);
        next(i + 1, len, callback);
    }
}(0, arr.length, function (param) {
    setTimeout(function () {
        console.log(param + "----------" + param * Math.random());
    }, param);
}));

循环中执行setTimeout代码,1,2为并行,不保证执行顺序,效率高