1.1 JavaScript 类型

类型转换

强制类型转换

测试用例 \ 方法	''	' '	'abc'	'0'	'123'	'123.1'	'123.1.1'	'123.abc'	'123.1.abc'	'abc123'	'0x123'	'0X123'	123	123.1	0	291	291	NaN	true	false	null	undefined
String()	''	' '	'abc'	'0'	'123'	'123.1'	'123.1.1'	'123.abc'	'123.1.abc'	'abc123'	'0x123'	'0X123'	'123'	'123.1'	'0'	'291'	'291'	'NaN'	'true'	'false'	'null'	'undefined'
toString()	''	' '	'abc'	'0'	'123'	'123.1'	'123.1.1'	'123.abc'	'123.1.abc'	'abc123'	'0x123'	'0X123'	'123'	'123.1'	'0'	'291'	'291'	'NaN'	'true'	'false'	'Cannot read property 'toString' of null'	'Cannot read property 'toString' of undefined'
Boolean()	false	true	true	true	true	true	true	true	true	true	true	true	true	true	false	true	true	false	true	false	false	false
Number()	0	0	NaN	0	123	123.1	NaN	NaN	NaN	NaN	291	291	123	123.1	0	291	291	NaN	1	0	0	NaN
parseInt()	NaN	NaN	NaN	0	123	123	123	123	123	NaN	291	291	123	123	0	291	291	NaN	NaN	NaN	NaN	NaN
parseFloat()	NaN	NaN	NaN	0	123	123.1	123.1	123	123.1	NaN	0	0	123	123.1	0	291	291	NaN	NaN	NaN	NaN	NaN

强制类型测试方法

const fnArr = [
  String, 
  toString, 
  Boolean,
  Number, 
  parseInt, 
  parseFloat, 
]

const testArr = [
  '',
  ' ',
  'abc',
  '0',
  '123',
  '123.1',
  '123.1.1',
  '123.abc',
  '123.1.abc',
  'abc123',
  '0x123',
  '0X123',
  123,
  123.1,
  0,
  0x123,
  0X123,
  NaN,
  true,
  false,
  null,
  undefined
  // Symbol(123)
]

let arr = '| 测试用例 \\ 方法 |'

for (let v of testArr) {
  let n = ''
  if (typeof v === 'string') {
    n = `'${v}'`
  } else {
    n = `${String(v)}`
  }
  arr += ` ${n} |`
}

arr += '\n'

for (let v of testArr) {
  arr += '| :---: '
}

arr += '| :---: | :---: |\n'

for (let fn of fnArr) {
  console.log(fn)
  const res1 = []
  for (let val of testArr) {
    let v = null
    try {
      if (fn === toString) {
        v = val.toString()
      } else {
        v = fn(val)
      }
    } catch (error) {
      console.error(error.message)
      v = error.message
    }
    if (typeof v === 'string') {
      v = `'${v}'`
    }
    res1.push(v)
  }
  const res2 = `| ${fn.name}() | ${res1.join(' | ')} |\n`
  
  arr = arr + res2

}

console.log(arr)