change key's value across multiple objects at once in JS

Question

I have multiple objects that all have the same keys lets say each object has: name and position. The first object will start with position=0. The second object would have position=1. The third object would have position=2 and so on until we get to the 10th object that would have position=9.

I need a way to subtract 1 from every objects position (with only possible values being 0-9 so that 0-1=9)

Looking for a solution that handles all of them mathematically at once, not just re-writing out new values to assign to each key individually.

desoares · Accepted Answer · 2018-04-26 10:42:42Z

1

Suppose you have an array of JavaScript objects, you could use map:

var newObjs = objects.map(function (object) {
    object.position = (object.position === 9 ? 0 : object.position--);
    return object;
});

A better approach would be:

objects.forEach( function (object) {
    object.position--;
    object.position = object.position < 0 ? 9 : object.position;
});

edited Apr 26, 2018 at 10:42

answered Apr 26, 2018 at 1:24

desoares

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2 Comments

Badetv Over a year ago

This works great except for the part: "object.position === 9 ? 0" it doesn't keep all position values between 0 and 9. Anything that has position=0 when this function is ran is going to -1.

Badetv Over a year ago

Update on above comment, only issue with that part was reversing order of 9 and 0 :)

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