Determine the data type (typeof)

• Original : MDN-typeof

• Function : The typeofoperator returns a string indicating the type of the unevaluated operand.

• Method : typeof operandortypeof(operand)

  • operand: An expression representing an object or primitive value, the type of which will be returned.

• Description :

Here are the typeofpossible return values:

Types of	result
Undefined	‘undefined’
Null	‘object’
Boolean	‘boolead’
Number	‘number’
BigInt	‘bigint’
String	‘string’
Symbol	‘symbol’
Function	‘function’
Any other object	‘object’

• Code :

/**
 * @name typeof测试
 * @description 通过 typeof 检测各个数据类型的返回
 */
const test = {
    
    
  testUndefined: undefined,
  testNull: null,
  testBoolean: true,
  testNumber: 123,
  testBigInt: BigInt(1234), // 大于 2 的 53 次方算 BigInt
  testString: '123',
  testSymbol: Symbol(),
  testFunction: function() {
    
    
    console.log('function');
  },
  testObject: {
    
    
    obj: 'yes',
  },
  testObjectString: new String('String'),
  testObjectNumber: new Number(123),
}

console.log(typeof(test.testUndefined)); // undefined
console.log(typeof(test.testNull));      // object
console.log(typeof(test.testBoolean));   // boolean
console.log(typeof(test.testNumber));    // number
console.log(typeof(test.testBigInt));    // bigint
console.log(typeof(test.testString));    // string
console.log(typeof(test.testSymbol));    // symbol
console.log(typeof(test.testFunction));  // function
console.log(typeof(test.testObject));    // object
console.log(typeof(test.testObjectString));    // object
console.log(typeof(test.testObjectNumber));    // object