Clean way to check if a value is contained within a Javascript Array (not the entire object)

Question

Basically I have an array of files (which include file names and paths etc.) and I am trying to see if a file with the same pathname already exists in the array (even if the other variables are different).

If the value is found in that array I want to move on, if it is not I want to add that object to the array. Also giving me trouble is that the array is empty at first (so I can't even run my check function the first time without checking allFiles.length).

What I am doing is looping through the entire array, and setting a Boolean to true if I find the value contained in the array, then going on to use an if...else

I thought this would be simple but I guess I was mistaken. I came up with this method and I am wondering if there is a cleaner way to do it.

  var allFiles = [];

  //function is called giving me a file, then:


            if (!allFiles.length) {
                allFiles.push(file); //Seems like there should be a better way
            } else {
                for (var i = 0; i < allFiles.length; i += 1) {
                    var exists = false;
                    if (allFiles[i]['fileName'] == fileName) {
                        exists = true;
                        console.log('Already exists');
                        break;
                    }
                }
                if (exists) {
                    console.log('Remove the file');
                    exists = false;
                } else {
                    console.log('Adding File');
                    allFiles.push(file);
                }
            }

Maybe that is clean enough, I was just wondering if you know of a different route. Thanks

Malk · Accepted Answer · 2014-06-27 03:02:43Z

1

You can pretty much use all the cool ECMA 5 array iteration methods now. They are limited to IE9+ but if you really wanted to most have shims in the mozilla documentation.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array#Iteration_methods

So you have a few options. If all you want is to add the object if it does not exist:

if (!allFiles.some(function(f){ return f.filename===filename}))
  allFiles.push(file);

If you need to do something with the file then you could just pull the index:

var idx = allFiles.reduce(function(m,f,idx) { 
   return m || (f.filename===filename ? idx : null)
},null);

if (var foundFile = allFiles[idx]) { ... }

answered Jun 27, 2014 at 3:02

Malk

12k4 gold badges35 silver badges34 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

pdoherty926 · Accepted Answer · 2014-06-27 02:55:55Z

1

You can use Array.some to test for the presence of a given path:

var objs = [{name: 'foo', path: 'c:\lulz'}, {name: 'foo', path: 'c:\looolz'}];

var conditionallyAddObjToArr = function (arr, obj) { 
    if (!arr.some(function (_obj) { return obj.path === _obj.path; })) {
        return [].concat(arr, obj);
    } else {
        console.log('path is already present', obj.path);
        return arr;
    }
}

objs = conditionallyAddObjToArr(objs, {name: 'baz', path: 'c:\wat'});  // will be added
objs = conditionallyAddObjToArr(objs, {name: 'baz', path: 'c:\lulz'}); // won't be added

Fiddle

answered Jun 27, 2014 at 2:55

pdoherty926

10.5k5 gold badges47 silver badges75 bronze badges

Collectives™ on Stack Overflow

Clean way to check if a value is contained within a Javascript Array (not the entire object)

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related