JavaScript iterates through the array, executes the FN function for each element in the array, and passes the array index and elements as parameters

There are two main methods of traversal, i++ method and in keyword method

varlist = [1, 2, 3, 4, 5, 6,7,8];//var L = list.length; for(varIinchlist) {Console.log (list[i]);}//[finished in 0.3s]varlist = [1, 2, 3, 4, 5, 6,7,8];//var L = list.length; for(vari = 0; i < list.length; i++) {Console.log (list[i]);}//[finished in 0.5s]varlist = [1, 2, 3, 4, 5, 6,7,8];varL =list.length; for(vari = 0; I < L; i++) {Console.log (list[i]);}//[finished in 0.4s]

It is relatively more efficient to

functionEach (arr, fn) {//your implement   for(Indexincharr)  {fn (arr[index],index); }}//where the FN function can accept two parameters: item and Index//using the examplevararr = [' Java ', ' C ', ' php ', ' HTML '];functionoutput (item) {Console.log (item)}each (arr, output); //Java, C, PHP, HTML//using the examplevararr = [' Java ', ' C ', ' php ', ' HTML '];functionoutput (item, index) {console.log (index+ ': ' +Item)}  Each (arr, output); //0:java, 1:c, 2:php, 3:html

However, the actual output format and expectations are different and are still to be improved.

JavaScript iterates through the array, executes the FN function for each element in the array, and passes the array index and elements as parameters