判断类型.html

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    <title>Document</title>
    <script>
        function getParamType(param) {
            // 先判断是否能用typeof 直接判断
            let types1 = ['number', 'string', 'boolean', 'undefined', 'symbol', 'function']
            let type = typeof param;
            type = types1.indexOf(type);
            if (type !== -1) {
                return types1[type]
            }
            // 剩余的用instanceof判断
            switch (true) {
                case param instanceof Date:
                    return 'date'
                case param instanceof Array:
                    return 'array'
                case param instanceof Object:
                    return 'object'
                case null === param && !param:
                    return 'null'
                default:
                    return 'can not judge'
            }
        }
        console.log(getParamType(1)); // number
        console.log(getParamType('1')); // string
        console.log(getParamType(true)); // boolean
        console.log(getParamType(undefined)); // undefined
        console.log(getParamType(Symbol.for(2))); // symbol
        console.log(getParamType(() => 1)); // function
        console.log(getParamType([])); // array
        console.log(getParamType({})); // object
        console.log(getParamType(new Date())); // date
        console.log(getParamType(null)); // null
    </script>
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