Nesting array.some() in javascript - Stack Overflow

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I'm wondering about nested uses of Array.some(). Suppose the task is to determine whether three numbers in an array sum to a given value x. I tried the following, but it did not work:

return myArray.some(function(num1){
    myArray.some(function(num2){
       myArray.some(function(num3){
           return num1 + num2 + num3 === x;
       });
    });
 });

Any insight on this would be helpful, including why the above doesn't work.

I'm wondering about nested uses of Array.some(). Suppose the task is to determine whether three numbers in an array sum to a given value x. I tried the following, but it did not work:

return myArray.some(function(num1){
    myArray.some(function(num2){
       myArray.some(function(num3){
           return num1 + num2 + num3 === x;
       });
    });
 });

Any insight on this would be helpful, including why the above doesn't work.

• javascript

Share Improve this question Follow edited Mar 5, 2018 at 8:08 sabithpocker 15.6k11 gold badge4343 silver badges7777 bronze badges asked Mar 5, 2018 at 8:05 Brian EmbryBrian Embry 8122 silver badges88 bronze badges 1

• while you take all the same array, you may add the same value tree times, is it what you want, or is it just a bad example of an other problem? – Nina Scholz Commented Mar 5, 2018 at 8:13

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3 Answers 3

Sorted by: Reset to default 6

You should return the response of each nested myArray.some otherwise, the enclosing method will receive an undefined.

See the code below.

var myArray = [1, 3, 7, 21];
var x = 31;

var opt = myArray.some(function(num1) {
  return myArray.some(function(num2) {
    return myArray.some(function(num3) {
      return num1 + num2 + num3 === x;
    });
  });
});

console.log(opt);

If you use arrow functions then you can omit return if only one statement:

Arrow functions can have either a "concise body" or the usual "block body".

In a concise body, only an expression is specified, which bees the explicit return value. In a block body, you must use an explicit return statement.

So this should work:

myArray.some(num1 =>
  myArray.some(num2 =>
    myArray.some(num3 => 
        num1 + num2 + num3 === x;
    )));

You do not return the inner result to the outer callbacks.

return myArray.some(function(num1) {
    return myArray.some(function(num2) {
        return myArray.some(function(num3) {
            return num1 + num2 + num3 === x;
        });
    });
});

If you like to prevent adding same values from same indices, you could add a check, which allowes only values which are not at the same index.

return myArray.some(function(num1, i) {
    return myArray.some(function(num2, j) {
        return myArray.some(function(num3, k) {
            return i !== j && i !== k && num1 + num2 + num3 === x;
        });
    });
});

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