JavaScript - Filter Nested Arrays

Question

I'm trying to filter an array in javascript, and am struggling when the array is nested.

At the moment, the furthest I've been able to get is filtering a flat array:

var ID = 3

var arr = [{ id : 1, name: "a" }, { id : 2, name: "b" }, { id : 3, name: "c" }]

var result = arr.filter(function( obj ) {return obj.id == ID;});
alert(result[0].name);

Though the above doesn't work if the array looks like this instead:

var arr2 = [
    [{ id : 1, name: "a" },{ id : 2, name: "b" }],
    [{ id : 3, name: "c" },{ id : 4, name: "d" }]
]

The two examples can be found: https://jsfiddle.net/vjt45xv4/

Any tips for finding the appropriate result on the nested array would be much appreciated.

Thanks!

If the array looks like that instead, what do you want the result to be? (Or do you only ever want to find one object?) — Ry-
– Ry- ♦, Commented Sep 14, 2015 at 18:28
Apply the same filter you are using on your arr to each item in arr2 (since items in arr2 are arrays themselves) — nem035
– nem035, Commented Sep 14, 2015 at 18:29

John Strickler · Accepted Answer · 2015-09-15 12:43:45Z

13

Flatten the array then filter it:

arr.reduce(function(a,b) { return a.concat(b);  })
   .filter(function(obj) { return obj.id == ID; });

edited Sep 15, 2015 at 12:43

answered Sep 14, 2015 at 18:30

John Strickler

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Full Stack Alien · Accepted Answer · 2020-08-27 00:34:30Z

3

arr2.filter(function(obj) {

  obj.filter(function(d) { 

    if(d.id == ID) { 

      result = d;

    }

  })

});

alert(result.name);

Hope this is what you were looking for. Rather than flattening the data here I went into the nested array till the point where it was flat(and matching) and set the result there.

arr2.forEach(function(d) {

  d.forEach(

    function(dd){ 

      alert(dd.id);

      if (dd.id==ID){

        result=dd; 

      }

    }

  );

});

alert(result.name);

Edit: As minitech mentioned its same working if just using forEach.

edited Aug 27, 2020 at 0:34

Full Stack Alien

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answered Sep 14, 2015 at 18:49

hunters30

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2 Comments

Ry- Over a year ago

If you’re going to assign to a variable, why not just use forEach?

hunters30 Over a year ago

Yep no argument there it can be done ! Besides I guess the way John Strickler mentioned is correct way if not looking for workaround.

user1529413 · Accepted Answer · 2021-12-26 08:38:32Z

I found this question from perhaps a similar problem:

I have a data structure such as this:

x.suites[0].specs[0].tests[0].results[0].status == "skipped"

My goal was to flag all of the non [skipped/ignored/???] status localed somewhere deep in this structure.

I came up with this solution:

var ignoreStatus = ["skipped"];
x.suites
.forEach( (xsuit)=> { xsuit.specs
    .forEach( (xspec)=> { xspec.tests
        .forEach( (xtst)=> { 
                var arry=xtst.results.filter((ftst)=>{ 
                    return !ignoreStatus.includes(ftst.status)
                });
                if(arry.length>0){ 
                    console.log(`!!!Flag this:${arry}`) 
                } else { 
                    console.log("ignored:" ,xtst.results.map(m=>{return m.status}).join("/") ); 
                } 
                
        })
    })
})

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