常用的 function 及 Pollyfills 整理

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functions

千分位

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function format(num) {
  num = num + '';
  return num.replace(/\B(?=(?:\d{3})+(?!\d))/g, ',');
}

pollyfills

Array.prototype.slice()

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Array.prototype.slicePollyfill = function() {
	var start = 0,
	end = this.length
	if (arguments.length === 1) {
		start = arguments[0]
	} else if (arguments.length >= 2) {
		start = arguments[0]
		end = arguments[1]
	} else {
		return this
	}
	var tmp = []
	for (var i = start; i < end; i++) {
		tmp.push(this[i])
	}
	return tmp
}

Array.prototype.find()

Code

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Array.prototype.myFind = function(fn){
	for(var i = 0; i < this.length; i++) {
		if (fn(this[i], i)) {
			return this[i]
		}
	}
}

Usage

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var arr = ['A', 'B', 'C']

arr.myFind(function (item, index) {
	return item === 'A'
})
// output: "A"