Check if value exists in an object in array of objects

Question

I am trying to write the code of following algorithm

• I have an array of active_id (array)
• ID coming from url (string)
• if value of ID does not exist in active_id array
  • run the function A()
• else do nothing.

Note - function A() should be run only once.

I tried writing the code

for (var i = 0; i < activeIds.length; i++) {
 if (activeIds[i] != uid) {
 A(); //This is running multiple times.
 }

I tried using while loop

var i = 0;
while (activeIds[i] != uid) {
 A(); //This is running multiple times again.
 i++;
}

There is something i am missing. not able to figure it out.

• mechanicals: Can you a add a fiddle link. People will be able to help you more easily.

Answer 1

You can just use indexOf function which will return -1 if element is not exist on array and positive number start 0 till array (length -1) if element exist:

if (activeIds.indexOf(uid) == -1) {
 A(); 
}
function A(); 

Answer 2

You can use indexOf, like this:

if( activeIds.indexOf(id) < 0 ) A();

Answer 3

If you want to invoke function A() only if the a particular ID (uid) does not exist in your array activeIds, you may want to alter your loop approach with this:

if (activeIds.filter(function(n){ return n===uid }).length==0){
 A();
}

Where you have a definition of function A() ready to use already.

Side note You syntax with function A(){} is just defining the function A but it's not going to run it. If you want to define and run it once, you may do:

(function A(){
 // logic goes here
})();

• RobG: I think every fits better: activeIds.every(function(v){return v != uid}).
• TaoPR: Just to make sure it works even if the browsers don't support ES6 feature. I'm not sure if activeIds.some(function(n){ return n===uid }) would produce better performance. Just wondering if it breaks as soon as it hits a truthy case.
• TaoPR: I thought too much BTW. Elements are just primitive numbers. :)
• RobG: filter and every are ES5 features. Only IE8 needs a shim...

Answer 4

You can use array.indexof() function in order to find the value. It will look something like that:

if(activeIds.indexOf(uid) === -1){
 A();
}

Answer 5

Try this, code.

var i=0;
var isMatchFound = false;
while (activeIds.length >= i) {
 if(activeIds[i] ==uid){
 isMatchFound = true;
 break;
}
 i++;
}
if(isMatchFound){
 //Call Function A
 A();
}

Hope this will help