js typeof 判斷型別

JavaScript 的內建七種型別有 number、string、boolean、null、undefined、object、symbol

string

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var title="這是測試";
console.log(typeof title)
'string'

number

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var numberValue = 1;
typeof numberValue
'number'

Object

var lists= [
    {title:'首頁',href:'home'},
    {title:'關於我',href:'about_us'},
    {title:'登入',href:'login'},
];
typeof lists
'Object'

boolean

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var isOpen = true;
typeof isOpen
'boolean'

undefined

1 2	typeof i 'undefined'

symbol

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const sym1 = Symbol();
typeof sym1
'symbol'

null

const foo = null;
if(foo == null){ 
    console.log('null')
}
typeof foo;
'symbol'