I have an interceptor function that I can put some javascript code into (for swagger ui). I only have one place to put in javascript code and it will be re-run frequently. I need to add a mutating observer in there, and have it only be setup one time.
There are many examples of how to do a Javascript method that will allow your code to be only run once. Here is a popular example: Function in JavaScript that can be called only once
But it assumes that you have somewhere to put the function where it will only be called once.
Is there a way to have my javascript code (not necessarily a function) only be run once? (So I don't end up setting up a bunch of mutating observers?)
To illustrate with an example, here is the code from the question I linked to, but copied in twice to show that it would be run many times:
var something = (function() {
var executed = false;
return function() {
if (!executed) {
executed = true;
console.log("hello");
}
};
})();
something(); // "do something" happens
something(); // nothing happens
var something = (function() {
var executed = false;
return function() {
if (!executed) {
executed = true;
console.log("hello");
}
};
})();
something(); // "do something" happens
something(); // nothing happens
The output of this code is:
hello
hello
Because the function is initalized twice, the call to console.log happens twice.
I need some way to have my code only happen once, with only one place to declare it.
For browser environment, you can use localStorage to set the value.
// make sure to initialize with true in your main entry point, otherwise the function would not run for the first time
localStorage.setItem('run-function', true);
const run = localStorage.getItem('run-function');
function test() {
if (run) {
console.log('ran function');
// ran once, set the value to false to prevent dupes
localStorage.setItem('run-function', false);
} else {
console.log('function already called once, exiting');
}
}
test();if you're on node.js environment you can make use of the global variable
// make sure to initialize with true in your main entry point, otherwise the function would not run for the first time
global.run_function = true;
function test() {
if (global.run_function) {
console.log('ran function');
global.run_function = false;
} else {
console.log('function already called once, exiting');
}
}
test();What about storing executed value in document ... it is created once at execution ... it could be stored in window (i.e. global var) but I think it is better to be kept in document. I'm not familiar with swagger but docuument should always exits I think. Storing it in localStorage will keep it longer than you may need and you should reset it on each run.
var something = (function() {
return function() {
if (!document.executed) {
document.executed = true;
console.log("hello");
}
};
})();
something(); // "do something" happens
something(); // nothing happens
var something = (function() {
return function() {
if (!document.executed) {
document.executed = true;
console.log("hello");
}
};
})();
something(); // "do something" happens
something(); // nothing happens