js upload pictures and get color codes

Part of js code

<script type="text/javascript">
	(() => {
		let obj = {};
		//获取DOM对象的方法
		let $ = function(id){
			return document.getElementById(id);
		}
		//获取预览图片路径
		let getObjectURL = function(file){
			let url = null ; 
			if (window.createObjectURL!=undefined) { // basic
				url = window.createObjectURL(file) ;
			} else if (window.URL!=undefined) { // mozilla(firefox)
				url = window.URL.createObjectURL(file) ;
			} else if (window.webkitURL!=undefined) { // webkit or chrome
				url = window.webkitURL.createObjectURL(file) ;
			}
			return url ;
		}
		//十六进制转换器
		let hexadecimal = function(num) {
			var r = parseInt(num).toString(16);
			if (r.length == 1) {
				return '0' + r;
			}
			return r.toUpperCase();
		}
		//判断颜色是否已存在
		let checkHasColor = function(arr, r, g, b) {
			for (var i = 0; i < arr.length; i++) {
				var n = equalsColor(arr[0], arr[1], arr[2], r, g, b);
				if (n >= 0.8) {
					return true;
				}
			}
			return false;
		}
		//判断相同颜色
		let equalsColor = function(r1, g1, b1, r2, g2, b2) {
			return (255 - Math.abs(r1 - r2) * 0.297 - Math.abs(g1 - g2) * 0.593 - Math.abs(b1 - b2) * 0.11) / 255;
		}
		//建立canvas画布
		let canvas = function(obj,size,param){
			let canvas = document.createElement("canvas");
			if (!canvas.getContext) {
				alert("很遗憾，您浏览器版本太老了，无法使用我们的小工具 ！");
				return;
			}
	})()
</script>