How to loop through array and find if key

Question

So basically I want o loop through an error (what i already did) and print the other key

var planet = "sun";
var planets = [{
    type: "sun",
    desc: "sun"
}, {
    type: "moon",
    desc: "moon"
}];

var pln = planets.length; 
for (var i = 0; i < pln; i++) {
    console.log(planets[i]);
}

How can i I find out if the var planet is in the array planets and print out the description from that key if so?

So, here you want to find the object that has the type of "sun", and print out the other object's type ("moon")? — David Thomas
– David Thomas, Commented Mar 3, 2015 at 22:16

dfsq · Accepted Answer · 2015-03-03 22:16:26Z

4

Compare planet with current planets[i].type. Once planet is found in array remember to terminate loop using break keyword:

var pln = planets.length; 
for (var i = 0; i < pln; i++) {
    if (planets[i].type === planet) {
        console.log(planets[i].desc);       
        break;     
    }
}

answered Mar 3, 2015 at 22:16

dfsq

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Comments

Travis J · Accepted Answer · 2015-03-03 22:51:56Z

2

You could use filter

var planet = "sun";
var planets = [{
        type: "sun",
        desc: "sun"
        }, {
        type: "moon",
        desc: "moon"}];

var planetObj = planets.filter(function(obj){ 
 return obj.type==planet;
})[0].desc;//sun

If you are unsure if planet exists, you may wish to see if the array returned from filter actually contained any elements, or perhaps iterate the returned set if there were more than one you were searching for.

edited Mar 3, 2015 at 22:51

answered Mar 3, 2015 at 22:19

Travis J

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4 Comments

dfsq Over a year ago

It can be just return obj.type == planet, if is not needed.

Travis J Over a year ago

@dfsq - Yes, not sure why I wrote it as if(){}.

blex Over a year ago

That's going to cause an error if the planet in not in the array. You need to check that the filter returned something before trying to access its desc property.

Travis J Over a year ago

@blex - Yes, but the OP states that they already know the element is there. This is just showing concept, I am not going to write a whole framework as an answer :) Please see edit indicating the need for error checking.

KJ Price · Accepted Answer · 2015-03-03 22:24:43Z

1

Hmm, I think this is what you want:

var pln = planets.length;
for (var i = 0; i < pln; i++) {
      if (planets[i].type == planet) {
          console.log(planets[i].desc);
          break;
      }
  }

edited Mar 3, 2015 at 22:24

answered Mar 3, 2015 at 22:17

KJ Price

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8 Comments

Etheryte Over a year ago

What's the point of simply copying the code of another answer? You forgot to copy what pln is defined as so your code doesn't even work.

KJ Price Over a year ago

Ah, that's a good point. I'll add that. Of course, it leads to the problem that planets is still not defined and still wouldn't work. At some point, one would hope that the user would actually read the code and infer what is going on.

RobIII Over a year ago

How does this answer differ from this answer which was clearly posted earlier and is an exact copy (except the comparison === v.s. ==)? What value does this answer add? "Please provide a reason for the downvote" > I'd be surprised if it didn't get downvoted if I were you...?

KJ Price Over a year ago

I posted mine seconds after the answer mentioned. I added his break; because I thought it was a good idea, but I didn't need to add it. The pln was requested by @Nit. Not sure what I did wrong? Should I have removed my answer once I saw the answer mentioned? Thanks for helping me become a better member :)

KJ Price Over a year ago

Furthermore, I think that you and @Nit overlooked that my loop is the same as the OP, thus the only thing I really contributed was the if statement.

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