javascript forEach function implementation code_javascript skills

Copy code The code is as follows:

function forEach(object, block, context, fn) {
if (object == null) return;
if (!fn) {
if (typeof object == "function" && object.call) {
//Traverse ordinary objects
fn = Function ;
} else if (typeof object.forEach == "function" && object.forEach != arguments.callee) {
//If the target has implemented the forEach method, use its own forEach method (such as Array object of standard browser)
object.forEach(block, context);
return;
} else if (typeof object.length == "number") {
// If it is a class Array object or array object of IE
_Array_forEach(object, block, context);
return;
}
}
_Function_forEach(fn || Object, object, block, context);
};
function _Array_forEach(array, block, context) {
if (array == null) return;
var i = 0,length = array.length;
if (typeof array == "string") {
for (; i < length; i ) {
block.call(context, array.charAt(i), i, array);
}
} else{
for (;i < length; i ) {
block.call(context, array[i], i, array);
}
}
};
_Function_forEach = function(fn, object, block, context) {
// fn here is always Function
for (var key in object) {
//Only traverse local properties
if ( object.hasOwnProperty(key)) {
//Equivalent to block(object[key], key)
block.call(context, object[key], key, object);
}
}
};

Some examples from the original author (I jumped over the wall! ):

Copy code The code is as follows:

function print(el,index){
alert(index " : " el)
}
forEach ([1, 2, 3], print);
forEach ({a: "aa", b: "bb",c: " cc"}, print);
forEach ("Situ Zhengmei", print);
forEach(document.styleSheets,function(el){
if(el.href) alert(el.href)
});

[Ctrl A Select all Note: If you need to introduce external Js, you need to refresh to execute

]

Copy code

The code is as follows:

function Person(name, age) {
this.name = name || "";
this.age = age || 0;
};
Person.prototype = new Person;
var fred = new Person("Fred", 38);
fred.language = "English";//Extremely late binding
fred.wife = "Wilma";//Extremely late binding
forEach(fred,print)

[Ctrl A select all Note:

If you need to introduce external Js, you need to refresh to execute <script> function forEach(object, block, context, fn) { if (object == null) return; if (!fn) { if (typeof object == "function" && object.call) { //遍历普通对象 fn = Function; } else if (typeof object.forEach == "function" && object.forEach != arguments.callee) { //如果目标已经实现了forEach方法，则使用它自己的forEach方法（如标准游览器的Array对象） object.forEach(block, context); return; } else if (typeof object.length == "number") { // 如果是类数组对象或IE的数组对象 _Array_forEach(object, block, context); return; } } _Function_forEach(fn || Object, object, block, context); }; function _Array_forEach(array, block, context) { if (array == null) return; var i = 0,length = array.length; if (typeof array == "string") array = array.split(""); for (;i < length; i++) { block.call(context, array[i], i, array); } }; _Function_forEach = function(fn, object, block, context) { // 这里的fn恒为Function for (var key in object) { //只遍历本地属性 if (object.hasOwnProperty(key)) { //相当于 block(object[key], key) block.call(context, object[key], key, object); } } }; function print(el,index){ alert(index+" : "+el) } forEach ([1, 2, 3], print); forEach ({a: "aa", b: "bb",c: "cc"}, print); forEach ("司徒正美", print); forEach(document.styleSheets,function(el){ if(el.href) alert(el.href) }); </script>]