how to detect a function was called with javascript
I have a ja开发者_开发百科vascript function.
How to check:
if function was called ( in
<head></head>section have this function), then not to call the functionif function was not called ( in
<head></head>section haven't this function), then call the function
like require_once or include_once with PHP
Static variables
Here's how to create static (like in C) variables using self calling functions to store your static variables in a closure.
var myFun = (function() {
var called = false;
return function() {
if (!called) {
console.log("I've been called");
called = true;
}
}
})()
Abstract the idea
Here's a function that returns a function that only gets called once, this way we don't have to worry about adding boiler plate code to every function.
function makeSingleCallFun(fun) {
var called = false;
return function() {
if (!called) {
called = true;
return fun.apply(this, arguments);
}
}
}
var myFun = makeSingleCallFun(function() {
console.log("I've been called");
});
myFun(); // logs I've been called
myFun(); // Does nothingUse decorator pattern.
// your function definition
function yourFunction() {}
// decorator
function callItOnce(fn) {
var called = false;
return function() {
if (!called) {
called = true;
return fn();
}
return;
}
}
yourFunction(); // it runs
yourFunction(); // it runs
yourFunction = callItOnce(yourFunction);
yourFunction(); // it runs
yourFunction(); // null
This solution provides a side-effect free way for achieving your goal. You don't have to modify your original function. It works nice even with library functions. You may assign a new name to the decorated function to preserve the original function.
var myLibraryFunction = callItOnce(libraryFunction);
myLibraryFunction(); // it runs
myLibraryFunction(); // null
libraryFunction(); // it runs
var called = false;
function blah() {
called = true;
}
if ( !called ) {
blah();
}
You can use a global variable in a custom namespace to store whether the function has been called.
if(!window.mynamespace){
window.mynamespace={};
}
mynamespace.callMeOnlyOnce=function(){
if(mynamespace.alreadyCalled)return;
alert('calling for the first time');
mynamespace.alreadyCalled=true;
};
// alert box comes
mynamespace.callMeOnlyOnce();
// no alert box
mynamespace.callMeOnlyOnce();
If (!your_func.called) {
your_func.called = true;
your_func();
}
加载中,请稍侯......
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