require函数实现用一句话概括:
依次加载require的模块,然后监测script的onload事件,判断所有模块加载成功,执行require的callback, 如果只带一个参数且不是数组,就是加载成功后return 模块。
//标记已经加载成功的个数
var REQ_TOTAL = 0;
//模块导出
window.exports = {};
//记录各个模块的顺序
var exp_arr = [];
//判断是否数组
function isArray(param) {
return param instanceof Array;
}
//require 真正实现
function require(arr, callback) {
var req_list;
if(isArray(arr)) {
req_list = arr;
} else {
req_list = [arr];
}
var req_len = req_list.length;
//模块逐个加载
for(var i=0;i<req_len;i++) {
var req_item = req_list[i];
var $script = createScript(req_item, i);
var $node = document.querySelector('head');
(function($script) {
//检测script 的onload事件
$script.onload = function() {
REQ_TOTAL++;
var script_index = $script.getAttribute('index');
exp_arr[script_index] = exports;
window.exports = {};
//所有链接加载成功后,执行callback
if(REQ_TOTAL == req_len) {
callback && callback.apply(exports, exp_arr);
}
}
$node.appendChild($script);
})($script);
}
}
//创建一个script标签
function createScript(src, index) {
var $script = document.createElement('script');
$script.setAttribute('src', src);
$script.setAttribute('index', index);
return $script;
}
然后写了2个导出模块的js文件, 只写了最简单的exports实现
// define.js
exports.define = {
topic: 'my export',
desc: 'this is other way to define ',
sayHello: function() {
console.log('topic ' + this.topic + this.desc);
}
}
// define2.js
exports.define = {
name: 'xm',
age: 22,
info: function() {
console.log('topic ' + this.name + this.age);
}
}
测试使用
//测试demo
require(['../res/define.js', '../res/define2.js'], function(def, def2) {
def.define.sayHello();
def2.define.info();
});