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JavaScript-原型

prototype javascript

1

CaRDiaK · 技术社区 · 16 年前

我正在努力获得更好的JavaScript工作知识。所以,我买了Douglas Crockford的《JavaScript的好部分》一书。

谢谢你的帮助。

var stooge = { 
    "first-name": "Jerome",
    "last-name": "Howard",
    "nickname": "J", 
    "profession" : 'Actor' 
};

// below is augmenting
var st = stooge;
st.nickname = "curly";
// st.nickname and nick are the same because both are ref's to the same object 
var nick = st.nickname;


document.writeln(stooge['first-name']);  //expect Jerome -- this is "suffix" retrieval 
document.writeln(st.nickname); //expect "curly" -- this is "notation" retrieval
document.writeln(nick); //expect "curly"
document.writeln(stooge.profession); 


//PROTOTYPE EXAMPLE; 
if (typeof Object.create !== 'function')
{
    object.create = function(o) {
            var F = function () {}; 
            F.prototype = o; 
            return new F();
};
var another_stooge = Object.create(stooge);
another_stooge['first-name'] = 'Barry'; 
document.writeln(another_stooge['first-name']);
// the below should be inherited from the prototype therefore "Actor" 
document.writeln(another_stooge.profession);

2 回复 | 直到 16 年前

1

5

Ferdinand Beyer 16 年前

在指定给object.create的函数表达式末尾缺少右大括号,并且在中没有将object大写 object.create = function(o) {

//PROTOTYPE EXAMPLE; 
if (typeof Object.create !== 'function')
{
    Object.create = function(o) {  // <--- "Object" instead of "object"
        var F = function () {}; 
        F.prototype = o; 
        return new F();
    };
}  // <--- Closing brace was missing

2

3

Mark Rushakoff 16 年前

你似乎错过了这条线的右括号 object.create = function(o) { .... 我看到if语句和 var F = function () {}; ,但不是为 function(o) .

缺少右大括号确实会抑制输出,因为Javascript会假定(缺少的)右大括号之前的所有内容都是函数定义的一部分,而不是要执行的内容。