从深拷贝谈类型检测

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实现深拷贝, 思路: 判断待拷贝的属性是否为数组或对象然后递归

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function deepCopy (p, c = {}) {	
  for(let i in p) {
    if (typeof p[i] === 'object') {	
      c[i] = p[i].constructor === Array ? [] : {}
      deepCopy(p[i], c[i])
    } else {
      c[i] = p[i]	
    }
  }
  return c
}

const testP = {
  a: {
    a1: 'a1'
  },
  b: ['b1', {
    b2: 'b2'
  }],
  c: 'c'
}

const testRes = deepCopy(testP)

console.log(testRes)

typeof

  1. ‘number’
  2. ‘string’
  3. ‘boolean’
  4. ‘undefined’
  5. ‘null’
  6. ‘symbol’
  7. ‘object’
  8. ‘function’

其中数组和对象都会返回 ‘object’

instanceof

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[] instanceof Array //true
[] instanceof Object //true

Object.prototype.toString.call

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Object.prototype.toString.call([]) // '[object Array]'
Object.prototype.toString.call({}) // '[object Object]'
Object.prototype.toString.call(1) // '[object Number]'
Object.prototype.toString.call('1') // '[object String]'
Object.prototype.toString.call(true) // '[object Boolean]'