JavaScript forEach() traversal function usage and introduction_javascript skills

The forEach() function traverses the array from beginning to end. There are three parameters: array element, element index, and array itself (if it is a parameter, it is the array element, which is the value of the array.

var data=[1,2,3,4,5,6];
var sum=0;
data.forEach(function(v){//其中的v就是数组的值 123456
sum+=v;})
document.write(sum+"<br>");//打印出来是21
data.forEach(function(o,p,q){//分别对应：数组元素，元素的索引，数组本身
 q[p]=o+1;
})
document.write(data);

Note: forEach cannot be terminated before all elements are passed to the called function (but the for loop has a break method). If you want to terminate early, forEach must be placed in a try block and an exception can be thrown. If the function called by forEach() throws a foreach.break exception, the loop will terminate early:

function foreach(a,b,c){
 try{
  a.forEach(b,c);
}catch(e){
  if(e===foreach.break)return;
 else throw e;
}
}
foreach.break=new Error("StopIteration");

}