(书名：JavaScript从入门到精通)

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1.自定义获取数据类型

function typeOf(o){

    let _toString=Object.prototype.toString;

    let _type={

    "undefined":"undefined",

    "number":"number",

    "string":"string",

    "boolean":"boolean",

    "[object Function]":"function",

    "[object RegExp]":"regexp",

    "[object Math]":"math",

    "[object Array]":"array",

    "[object Date]":"date",

    "[object Error]":"error"

}

return _type[typeof o] || _type[_toString.call(o)] || (o instanceof Object?o.constructor.name:'object') || (o ? "object" : "null"); }