js常用工具函数

常用工具函数

• 数组判断

  • const isArray = (arg) => {
    	return Array.isArray(arg)
    }
    

  • const isArray = (arg) => {
    	return Object.prototype.toString.call(arg) === '[object Array]'
    }
    

  • const isArray = (arg) => {
    	delete Array.prototype.toString
    	return arg.toString() === '[object Array]'
    }
    

• 对象判断

  • const isObject = (arg) => {
    	return Object.prototype.toString.call(arg) === '[object Object]'
    }
    

  • const isObject = (arg) => {
    	return typeof arg === 'object' && arg.constructor === Object
    }
    

• 深拷贝

  • const deepClone = (arg) => {
    	if (isObject(arg)) {
    		let newArg = {}
    		let keys = Object.keys(arg)
    		for (let i = 0; i < keys.length; i++) {
    			let k = keys[i]
    			let v = arg[k]
    			let v1 = deepClone(v)
    			newArg[k] = v1
    		}
    		return newArg
    	} else if (isArray(arg)) {
    		let newArg = []
    		for (let i = 0; i < arg.length; i++) {
    			let v = arg[i]
    			let v1 = deepClone(v)
    			newArg.push(v1)
    		}
    		return newArg
    	} else {
    		return arg
    	}
    }
    

  • const deepClone = (c, p) => {
    	let c = c || {}
    	for (let k in p) {
    		if (typeof p[k] === 'object') {
    			c[k] = p[k].constructor === Array ? [] : {}
    			deepClone(c[k], p[k])
    		} else {
    			c[k] = p[k]
    		}
    	}
    	return c
    }
    

• 对象删除

  • const removeProperty = (target,propertyToRemove) => {
        const {[propertyToRemove]: _, ...newTarget} = target
        return newTarget
    }
    
    

• 判断是否相等

  • const equals = (m, n) => {
    	if (isArray(m) && isArray(n)) {
    		if (m.length !== n.length) {
    			return false
    		}
    
    		for (let i = 0; i < m.length; i++) {
    			let mVal = m[i]
    			let nVal = n[i]
    			if (!equals(mVal, nVal)) {
    				return false
    			}
    		}
    		return true
    	} else if (isObject(m) && isObject(n)) {
    		let mkeys = Object.keys(m)
    		let nkeys = Object.keys(n)
    		if (mkeys !== nkeys) {
    			return false
    		}
    		for (let i = 0; i < mkeys.length; i++) {
    			let km = mkeys[i]
    			let kn = nkeys[i]
    			let mVal = m[km]
    			let nVal = n[kn]
    			if (km !== kn) {
    				return false
    			}
    			if (!equals(mVal, nVal)) {
    				return false
    			}
    		}
    		return true
    	} else {
    		return m === n
    	}
    }
    

• 判断对象和数组可以使用Object的原型方法toString, 对于对象来说 Object.prototype.toString().call(arg) === arg.toString(), 对于数组和函数来说,作为Object的原型都重写了toString方法,可通过delete删除重写的toString,在使用toString方法

• toString: 每个对象都有一个 toString() 方法，当该对象被表示为一个文本值时，或者一个对象以预期的字符串方式引用时自动调用。默认情况下，toString() 方法被每个 Object 对象继承。如果此方法在自定义对象中未被覆盖，toString() 返回 "[object type]"，其中 type 是对象的类型。