prototype 的作用

[vuqrzk5w]

// This is a constructor function that initializes new Range objects.
// Note that it does not create or return the object. It just initializes this.
function Range(from, to) {
    // Store the start and end points (state) of this new range object.
    // These are noninherited properties that are unique to this object.
    this.from = from;
    this.to = to;
}

// All Range objects inherit from this object.
// Note that the property name must be "prototype" for this to work.
Range.prototype = {
    // Return true if x is in the range, false otherwise
    // This method works for textual and Date ranges as well as numeric.
    includes: function(x) { return this.from <= x && x <= this.to; },
    // Invoke f once for each integer in the range.
    // This method works only for numeric ranges.
    foreach: function(f) {
        for(var x = Math.ceil(this.from); x <= this.to; x++) f(x);
    },
    // Return a string representation of the range
    toString: function() { return "(" + this.from + "..." + this.to + ")"; }
};

这里用Range.prototype = {...

和

// This is a constructor function that initializes new Range objects.
// Note that it does not create or return the object. It just initializes this.
function Range(from, to) {
    // Store the start and end points (state) of this new range object.
    // These are noninherited properties that are unique to this object.
    this.from = from;
    this.to = to;

// Return true if x is in the range, false otherwise
    // This method works for textual and Date ranges as well as numeric.
    includes: function(x) { return this.from <= x && x <= this.to; },
    // Invoke f once for each integer in the range.
    // This method works only for numeric ranges.
    foreach: function(f) {
        for(var x = Math.ceil(this.from); x <= this.to; x++) f(x);
    },
    // Return a string representation of the range
    toString: function() { return "(" + this.from + "..." + this.to + ")"; }
}
;

有啥区别啊?

[zhjdg]

你第二段代码不报错吗？

[似梦飞花]

你确定你那样写能正常运行？

[oN5GrzoN]

引用 4 楼 yyl8781697 的回复:

prototype 可以对 对象 添加属性和方法 你第二段代码是不正确的

		// This is a constructor function that initializes new Range objects.
// Note that it does not create or return the object. It just initializes this.
function Range(from, to) {
    // Store the start and end points (state) of this new range object.
    // These are noninherited properties that are unique to this object.
    this.from = from;
    this.to = to;
 
// Return true if x is in the range, false otherwise
    // This method works for textual and Date ranges as well as numeric.
    this.includes= function(x) { return this.from <= x && x <= this.to; };
    // Invoke f once for each integer in the range.
    // This method works only for numeric ranges.
    this.foreach= function(f) {
        for(var x = Math.ceil(this.from); x <= this.to; x++) f(x);
    },
    // Return a string representation of the range
    this.toString= function() { return "(" + this.from + "..." + this.to + ")"; };
};

Javascript Prototype

那,这样,和加在Prototype上,有啥区别啊?

[街道向晚]

引用 5 楼 oN5GrzoN 的回复:

[quote=引用 4 楼 yyl8781697 的回复:] prototype 可以对 对象 添加属性和方法 你第二段代码是不正确的

		// This is a constructor function that initializes new Range objects.
// Note that it does not create or return the object. It just initializes this.
function Range(from, to) {
    // Store the start and end points (state) of this new range object.
    // These are noninherited properties that are unique to this object.
    this.from = from;
    this.to = to;
 
// Return true if x is in the range, false otherwise
    // This method works for textual and Date ranges as well as numeric.
    this.includes= function(x) { return this.from <= x && x <= this.to; };
    // Invoke f once for each integer in the range.
    // This method works only for numeric ranges.
    this.foreach= function(f) {
        for(var x = Math.ceil(this.from); x <= this.to; x++) f(x);
    },
    // Return a string representation of the range
    this.toString= function() { return "(" + this.from + "..." + this.to + ")"; };
};

Javascript Prototype

那,这样,和加在Prototype上,有啥区别啊?[/quote] 加prototype不同的对象，方法或参数共享同一个内存；直接在构造函数里面写不同的对象则调用不同的内存。

[阿鱼]

[yyl8781697]

prototype 可以对 对象 添加属性和方法 你第二段代码是不正确的

		// This is a constructor function that initializes new Range objects.
// Note that it does not create or return the object. It just initializes this.
function Range(from, to) {
    // Store the start and end points (state) of this new range object.
    // These are noninherited properties that are unique to this object.
    this.from = from;
    this.to = to;
 
// Return true if x is in the range, false otherwise
    // This method works for textual and Date ranges as well as numeric.
    this.includes= function(x) { return this.from <= x && x <= this.to; };
    // Invoke f once for each integer in the range.
    // This method works only for numeric ranges.
    this.foreach= function(f) {
        for(var x = Math.ceil(this.from); x <= this.to; x++) f(x);
    },
    // Return a string representation of the range
    this.toString= function() { return "(" + this.from + "..." + this.to + ")"; };
};

Javascript Prototype