var foo = new Object(); var bar = new Object(); var map = new Object(); map[foo] = "foo"; map[bar] = "bar"; // Alerts "bar", not "foo". alert(map[foo]);
当对象作为key的时候,会自动调用对象的 toString 方法,比如
map[foo]相当于 map[foo.toString()]即是 map["[object Object]"] 。
可以重写toString方法
// (1) Look up value by name: map.meaning_of_life; // (2) Look up value by passing the key as a string: map["meaning_of_life"]; // (3) Look up value by passing an object whose toString() method returns a // string equivalent to the key: var machine = new Object(); machine.toString = function() { return "meaning_of_life"; }; map[machine];
单引号和双引号的作用是相同的,在严格的JSON中,要使用双引号。同时最后一个key-value之后不能有逗号
function hereOrThere(){ return'here'; } alert(hereOrThere());// alerts 'there' function hereOrThere(){ return'there'; }
var hereOrThere = function() { return 'here'; }; alert(hereOrThere()); // alerts 'here' hereOrThere = function() { return 'there'; };
var a=1; function test(){ console.log(a); var a=2; console.log(a); }
输出结果
JS 将参数arguments 转为数组 例如 name=Array.prototype.splice.call(arguments,0)
var set='ddd';
function set(){
console.log("hello");
};
set();
提示错误 string not a function