console.time () and console.timeEnd () can print the execution time of the program.
(function(){
console.time("index");
var div = document.getElementById("div");
div.onclick = function(){
alert("123");
};
console.timeEnd("index");
}());question: why is the time printed when it is not clicked?
because div.onclick = function () {.} is just an assignment operation.
in your code, console.time only counts the time taken by
var div =. (ignoring the behavior of getBy. , simplifying the problem)
div.onclick =.
these two assignment operations.
console.timeEnd ('index'); not in the click event. The click event in
code only executed alert (' 123');