How to run an array through a filter in js?

Question

I have the following code.

var eqn = c1 + q1 + q2 +  ‘ + ‘ + c2 + w1 + w2 + ‘=‘ + c3 + e1 + e2;

This code combines strings not add numbers.

I think it would be best to modify this string by using an array which I can do. My question is I want to remove the variable if it equals 1. For example if c1 == 1 then the variable should be defined like this: var eqn = q1 + q2 + ‘ + ‘ + c2 + w1 + w2 + ‘=‘ + c3 + e1 + e2; I want this to happen to any one or more variable that is equal to one. Is there a function or piece of code that can be used to do this?

@GeorgeJempty Sorry my mistake, take a look at the updated question — Riz-waan
– Riz-waan, Commented Nov 23, 2017 at 1:30
there is + operator missing, and btw. what are you doing? concatenating stirngs or adding numbers? If this is a mix, it will end up in an unexpected result: 2 + 2 + " + " + 3 + 3 check your console.. — webdeb
– webdeb, Commented Nov 23, 2017 at 1:41
Use parentheses to make it clear and better readable: (2 + 2) + " + " + (3 + 3) — webdeb
– webdeb, Commented Nov 23, 2017 at 1:42

klugjo · Accepted Answer · 2017-11-23 13:04:18Z

3

You can use Array.reduce

var string = [c1, q1, q2, ' + ', c2, w1, w2, ' = ', c3, e1, e2]
  .reduce((acc, cur) => cur == 1 ? acc : acc + '' + cur, '');

Example:

The following values

1 + 2 + 3 + ' + ' + 4 + 5 + 6 + ' = ' + 7 + 8 + 9;

will return

'23 + 456 = 789'

edited Nov 23, 2017 at 13:04

answered Nov 23, 2017 at 1:34

klugjo

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8 Comments

Colin Over a year ago

Very pretty! But maybe make sure you coerce it to a string or c1 and q1 will add mathematically. ...? acc : '' + acc + cur

Riz-waan Over a year ago

@klugjo Does that mean when I run console.log(string); will I get one fluent string?

kamoroso94 Over a year ago

That's nice! I would have filtered then joined. I like your method though.

webdeb Over a year ago

would't it be prefixed with "undefined", you should probably define the initial acc.

Riz-waan Over a year ago

@klugjo q1, w1, and e1 are letters/words, would this method still work?

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Dexygen · Accepted Answer · 2017-11-23 01:35:40Z

0

OK so under the assumption that the variables are numeric you could run them all through a function such as the following, which will return zero if it contains one, and the arithmetic will work out:

function excludeIfOne(val) {
    return val === 1 ? 0 : val
}

This could however lead to one long messy line of code. See the other answer suggesting the use of reduce, which I was about to suggest myself

answered Nov 23, 2017 at 1:35

Dexygen

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Comments

kamoroso94 · Accepted Answer · 2017-11-23 01:52:35Z

0

If you are not familiar with reduce, you can using filter and join.(likes klugjo's way)

var string = [c1, q1, q2, ' + ', c2, w1, w2, '+', c3, e1, e2];
string.filter(word=> word!=1).join('');

edited Nov 23, 2017 at 1:52

kamoroso94

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answered Nov 23, 2017 at 1:42

ChunTingLin

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2 Comments

klugjo Over a year ago

typo: use filter instead of map

ChunTingLin Over a year ago

Thanks for indicating my fault.

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