Find in first array values and then change them with values from another array

Question

First array

var danu = ["nu", "da", "nu", "da", "da", "da", "da", "da", "da", "nu", "nu"];

Second array

var abc2 = ["2", "3", "2", "3", "3", "2", "2"];

I want to replace all "da" from first array with the values from the second array 1 by 1 so i will get

["nu", "2", "nu", "3", "2", "3", "3", "2", "2", "nu", "nu"];

I want the fix only in Javascript. I tried using the loop metod

for (i=0; i<danu.length; i++) {
if (danu[i] == "da") {
 danu[i] = abc2[i];
}
}

But i end up getting the array to this

["nu", "3", "nu", "3", "3", "2", "2", undefined, undefined, "nu", "nu"]

I tried looping through but i don't know exactly how should i do to work. — Pinguluk
– Pinguluk, Commented Dec 11, 2015 at 21:06
Welcome to SO. Please visit the help center to see how and what to ask here. Hint: Use a for loop or some of the array prototype methods developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/… — mplungjan
– mplungjan, Commented Dec 11, 2015 at 21:08
if ( value equals ) Replace value with first value from other array, increment counter. — epascarello
– epascarello, Commented Dec 11, 2015 at 21:08

Spencer Wieczorek · Accepted Answer · 2015-12-11 21:41:32Z

2

You can use .map to apply changes on each item in the danu array. Then have a c count which increments when "da" was found.

danu = ["nu", "da", "nu", "da", "da", "da", "da", "da", "da", "nu", "nu"];
abc2 = ["2", "3", "2", "3", "3", "2", "2"];

c = 0;

newArr = danu.map(function(e,i){
    if(e == 'da') return abc2[c++];
    return e;
});

console.log(newArr);

edited Dec 11, 2015 at 21:41

answered Dec 11, 2015 at 21:09

Spencer Wieczorek

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3 Comments

mplungjan Over a year ago

Could you not start at 0 and return abc2[c++]; ?

Spencer Wieczorek Over a year ago

@mplungjan That's a good point, I've added that into my answer. Thank you.

Spencer Wieczorek Over a year ago

@mplungjan For the second method you will want to use shift rather than pop. jsfiddle.net/90jgjekd/4

Nina Scholz · Accepted Answer · 2015-12-11 21:15:39Z

1

Just use Array.prototype.reduce():

var danu = ["nu", "da", "nu", "da", "da", "da", "da", "da", "da", "nu", "nu"],
    abc2 = ["2", "3", "2", "3", "3", "2", "2"];
  
danu.reduce(function (r, a, i, o) {
    o[i] = a === 'da' ? abc2[r++] : a;
    return r;
}, 0);

document.write('<pre>' + JSON.stringify(danu, 0, 4) + '</pre>');

answered Dec 11, 2015 at 21:15

Nina Scholz

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1 Comment

Nina Scholz Over a year ago

@mplungjan, yes, map is shorter for a new array, but this solution works in situ.

Branden Keck · Accepted Answer · 2015-12-11 21:08:38Z

0

Assuming that the second array is equal in length to the number of "da" in the first array, the code would look like:

var j = 0;
for(int i; i<danu.length; i++){
    if(danu[i] === "da"){
        danu[i] = abc2[j];
        j = j + 1;
    }
}

However, if the second array is of different length, incrementing j could put abc2 out of bounds. You would need a different strategy based on what you are actually trying to accomplish with this.

answered Dec 11, 2015 at 21:08

Branden Keck

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1 Comment

Pinguluk Over a year ago

Hm, it doesn't work. I get unexpected identifier error...but thanks anyway, i got the fix from previous answer.

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