Jquery: extending array within each loop

Question

I'm filtering a an array in Jquery depending of some button selections of the user. I loop over the possibilities and build a "result" array extending it with a "original_array" slice.

result = []
$.each(university_selection, function(index, value) {
     if ($(value).attr('name') == 'on') {
          partial = jQuery.grep(original_array, function(n) { return ( n.institucion == $(value).text()); });
          result = $.extend( result , partial )
     };
});

The filterign works fine, but the "extend" command seems to replace previous instance instead of "accumulating". I only get the last slice returned.

I guess it has something to do with the moment in which the "result = $.extend( result , partial )" is stored in memory.

Any clues?

CertainPerformance · Accepted Answer · 2020-01-12 02:40:10Z

1

To tweak your jQuery, you can push each item in partial to result:

result.push(...partial);

or

result = result.concat(partial)

But the overall code is kinda verbose, not very functional, and more computationally complex than it needs to be.

To reduce the computational complexity from O(n^2) to O(n), construct a Set of the on values, then .filter the original_array by whether the institucion property is included. The logic will probably be a lot clearer to follow as well:

const selectedValues = new Set(
  [...university_selection]
    .filter(elm => elm.name === 'on')
    .map(elm => elm.textContent)
);
const result = original_array.filter(item => selectedValues.has(item.institucion));

This way, you only iterate over the original_array once, and a plain .filter constructs the result array based on a simple condition.

edited Jan 12, 2020 at 2:40

answered Jan 11, 2020 at 23:30

CertainPerformance

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Comments

Francisco Ghelfi · Accepted Answer · 2020-01-12 02:28:35Z

0

I could resolve the issue using

result = result.concat( partial );

answered Jan 12, 2020 at 2:28

Francisco Ghelfi

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