How to push value of array if defined?

Question

I have an array which has a list of items that will be returned as undefined if none come back and true if it does.

resolved = [undefined, undefined, undefined, true, undefined]

if there is a 'true' item in the Array how would I push it into a new array?

I have this so far.

resolved.map(item =>{

  if(item === undefined){
    console.log(`No resolved issues`);
  } else {
    console.log(`defined`);
  }

} )

output:

newResolved = [true]

resolved = [undefined, undefined, undefined, true, undefined]

resolved.map(item =>{
    
      if(item === undefined){
        console.log(`No resolved issues`);
      } else {
        console.log(`defined`);
      }
    
    } )

resolved.filter(Boolean)? resolved.some(Boolean)? Welcome to SO! — ggorlen
– ggorlen, Commented Oct 26, 2020 at 4:09
Unclear what you actually want. What is the output/other array? — epascarello
– epascarello, Commented Oct 26, 2020 at 4:09

charlietfl · Accepted Answer · 2020-10-26 04:11:43Z

1

You are using map() incorrectly as you need a return every iteration to the new array it creates

What you are really wanting is filter()

const arr = [undefined, undefined, undefined, true, undefined];

const res = arr.filter(e => e===true)

console.log(res)

answered Oct 26, 2020 at 4:11

charlietfl

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1 Comment

epascarello Over a year ago

.filter(Boolean)

Derek Wang · Accepted Answer · 2020-10-26 04:16:10Z

1

You can use Array.prototype.filter function to filter valid items only.

const resolved = [undefined, undefined, undefined, true, undefined];

const result = resolved.filter(item => item);
console.log(result);

answered Oct 26, 2020 at 4:16

Derek Wang

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Comments

ckesplin · Accepted Answer · 2020-10-26 04:21:19Z

0

You're headed down the right path, I think. This looks like a prime use of the forEach method instead of the map method. This will allow you to look at each array value and do something with it.

const newArray = []

resolved.forEach(item =>{
  if(item === undefined){
    console.log(`No resolved issues`);
  } else {
    console.log(`defined`);
    newArray.push(item)
  }
})

answered Oct 26, 2020 at 4:21

ckesplin

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