如果i是挂在全局上的,因为他每次loop完都要从全局中找回i值,i++ 和 判断 而封装在 function里面的,对比与在全局里找i,单单在function 里找起来比较快 ——《javascript循环时间判断优化!》 从性能上考量,我从eslint上禁止 for in。 之前在gem代码重构的过程中,讲了很多次 for in for map foreach等遍历情...
letoption={tooltip:{show:true,formatter:function(params){if(params.value.length>1){return" "+params.name+":"+params.value[2];}else{return" "+params.name+":"+(params.value||0);}},},geo:{map:"china",zoom:1.2,show:true,roam:false,emphasis:{label:{show:false,},},layoutSize:"100%...
{/* … */})// 回调函数flatMap(callbackFn)flatMap(callbackFn,thisArg)// 行内回调函数flatMap(function(currentValue){/* … */})flatMap(function(currentValue,index){/* … */})flatMap(function(currentValue,index,array){/* … */})flatMap(function(currentValue,index,array){/* … */}...
require(["esri/layers/MapImageLayer"], function(MapImageLayer){ // points to the states layer in a service storing U.S. census data let layer = new MapImageLayer({ url: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/Census/MapServer" }); map.add(layer); // adds the ...
firstconstsecond=newMap([[1,"uno"],[2,"dos"],]);// Map 对象同数组进行合并时,如果有重复的键值,则后面的会覆盖前面的。constmerged=newMap([...first,...second,[1,"eins"]]);console.log(merged.get(1));// einsconsole.log(merged.get(2));// dosconsole.log(merged.get(3));// thre...
1let array = arr.map(functioncallback(currentValue, index, array) {2//Return element for new_array3}[, thisArg]) 参数Edit callback 生成新数组元素的函数,使用三个参数: currentValue callback的第一个参数,数组中正在处理的当前元素。 index ...
fruits.forEach(function(value, key) { text += key +' = '+ value; }) Try it Yourself » Map.entries() Theentries()method returns an iterator object with the [key,values] in a map: Example // List all entries lettext =""; ...
for...in会遍历出原型对象上的属性 Object.prototype.objCustom = function() {}; Array.prototype....
//定义一个函数,使得传入的每一个值都加上2functionadd2(x,y,z){ console.log(x+"=="+y+'=='+z);returnx + 2}//定义一个数组vararr = [1,2,3,4,5,6]varnewArr =arr.map(add2) console.log(newArr); 打印结果 1==0==1,2,3,4,5,6 ...
allLayers.find(function(layer) { return layer.title === "US Counties"; }); // Create a filtered collection of the non-group layers const nonGroupLayers = map.allLayers.filter(function(layer) { return !foundLayer.layers; }); // Listen for any layer being added or removed in the Map...