Comparing two arrays and push in another array wrong position element

Question

I got two arrays, both type string :

var correctAnswers = ["0", "1", "2", "3", "4", "5"];

and second :

var finalArray = ["0", "1", "4", "3", "5", "2"];

I would like to compare them and and if not match second with first to extract elements and push them in another array, like this :

finalArray = ["0", "1", "3"];

var toChange = ["4", "5", "2"];

Do you also want to store the index/position of the incorrect answers? — Terry
– Terry, Commented May 5, 2014 at 10:08
Nope, position doesnt need to be same. Just to push elements that doesnt match position and number with correctAnswer array into toChange array. — user3459377
– user3459377, Commented May 5, 2014 at 10:10
@user3459377 There is no dumb question. Just lazy questions. — Terry
– Terry, Commented May 5, 2014 at 10:13

A. Wolff · Accepted Answer · 2014-05-05 10:26:40Z

1

You could use jQuery map method too:

var toChange = $.map(finalArray, function(v, k){
    return correctAnswers[k] !== v ? v: null;
});

finalArray = $.map(finalArray, function(v, k){
    return correctAnswers[k] === v ? v: null;
});

DEMO

Or using array.prototype.filter():

var toChange = finalArray.filter(function(v, k){
    return correctAnswers[k] !== v;
});

finalArray = finalArray.filter(function(v, k){
    return correctAnswers[k] === v;
});

filter DEMO

edited May 5, 2014 at 10:26

answered May 5, 2014 at 10:20

A. Wolff

74.4k9 gold badges98 silver badges158 bronze badges

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

2 Comments

user3459377 Over a year ago

I've been running of using map, but it seems it work like a charm +1

A. Wolff Over a year ago

@user3459377 this is jQuery map method. Using array.prototype.map() wouldn't work as expected here, maybe that was your issue here. Indeed, you should use filter() instead.

Barmar · Accepted Answer · 2014-05-05 10:16:42Z

1

var toChange = [];
for (var i = finalArray.length - 1; i >= 0; i--) {
    if (finalArray[i] !== correctAnswers[i]) {
        toChange.push(finalArray[i]);
        finalArray.splice(i, 1);
    }
}

The key to this is iterating down from the length to 0, rather than up from 0 to the length as usual. This is because splice changes the indexes of all the elements after the element being removed, so normal iteration would skip an element after each splice.

answered May 5, 2014 at 10:16

Barmar

789k57 gold badges555 silver badges669 bronze badges

Comments

XiozZe · Accepted Answer · 2014-05-05 10:16:58Z

1

This will do it:

http://jsfiddle.net/XiozZe/NkM6s/

var correctAnswers = ["0", "1", "2", "3", "4", "5"];
var finalArray = ["0", "1", "4", "3", "5", "2"];
var correctFinal = [];
var toChange = [];

for(var i = 0; i < correctAnswers.length; i++){
    if(correctAnswers[i] === finalArray[i]){
        correctFinal[correctFinal.length] = finalArray[i];
    }
    else{
       toChange[toChange.length] = finalArray[i];
    }   
}

answered May 5, 2014 at 10:16

XiozZe

4722 silver badges8 bronze badges

1 Comment

user3459377 Over a year ago

Also, great answer too!! Thanks for ur time

Yannick · Accepted Answer · 2014-05-05 10:32:41Z

First you've got to define your variables

// Define your variables
var correctAnswers = ["0", "1", "2", "3", "4", "5"];
var answers     =    ["0", "1", "4", "3", "5", "2"];
var finalArray = [];
var toChange = [];

Then you create a loop, which loops over the Answers array.

// comparing them could be done with a simple loop
for (var i = 0; i<answers.length; i++) {
    if (correctAnswers[i] == answers[i]) { //if they're equal, push the value into the final array
        finalArray.push(answers[i]);
    } else { // if not, push them into the toChange array
        toChange.push(answers[i]);
    }
}

This will give you toChange = [0, 1, 3] If you want toChange = [0, 1] you've got to change it to

toChange = answers.slice(0);

for (var i = 0; i<correctAnswers.length; i++) {
    if (correctAnswers[i] == Answers[i]) { //if they're equal, push the value into the final array and remove the first value from the toChange array
        finalArray.push(Answers[i]);
        toChange.shift();
    } else { // if not, break
        break;
    }
}

Fiddle

Collectives™ on Stack Overflow

Comparing two arrays and push in another array wrong position element

4 Answers 4

DEMO

filter DEMO

2 Comments

Comments

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

2 Comments

Comments

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related