Array filling in Javascript

Question

I need to fill 1 as an element of array FilteredRPeakThousandDataArray starting with index 500 in new array, and 0 for other index. Done like the following but the new array is getting filled only by 0. Explanation : at index 600,800,1200,1300 element in FilteredRPeakThousandDataArray should be 1 and 0 in all other indexes including for index 2(because 2 is less than 500)

var j = 500;
var FilteredRPeakDataArray = new Array();
var FilteredRPeakDataArray = [2, 600, 800, 1200, 1300];
var FilteredRPeakThousandDataArray = new Array();

for (var i = 0; i < 1500; i++) {
  if (FilteredRPeakDataArray[j] == i) {
    FilteredRPeakThousandDataArray[i] = 1;
  } else {
    FilteredRPeakThousandDataArray[i] = 0;
  }
  
  j++;
}

console.log("FilteredRPeakThousandDataArray " + FilteredRPeakThousandDataArray);

you don't have the position 500 on FilteredRPeakDataArray, so, just compare j==i — Roy Bogado
– Roy Bogado, Commented Jun 20, 2019 at 9:44

baao · Accepted Answer · 2019-06-20 09:46:02Z

2

You can simply use Array.from().

const FilteredRPeakDataArray = [2, 600, 800, 1200, 1300];

const FilteredRPeakThousandDataArray = Array.from({length: 1500},
 (_, i) => FilteredRPeakDataArray.includes(i) && i > 500 ? 1 : 0
);
console.log(FilteredRPeakThousandDataArray);

answered Jun 20, 2019 at 9:46

baao

73.5k18 gold badges152 silver badges208 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Eliran · Accepted Answer · 2019-06-20 09:46:05Z

you had two problems

one is that you were advancing J index anyway

and the main one was this line : FilteredRPeakDataArray[j] == i

FilteredRPeakDataArray was an array with only 5 elements and you were going with huge indices. there is better ways to implement what you trying to do but I guess you are new to js (or maybe coding) so this fix will give you a better understanding of what went wrong

var startFrom = 500;
var j=0;
var FilteredRPeakDataArray = new Array();
var FilteredRPeakDataArray = [2,600,800,1200,1300];
var FilteredRPeakThousandDataArray = new Array();

        for (var i=0;i<1500;i++){
      if(FilteredRPeakDataArray[j]==i){
if( i > startFrom ){
        FilteredRPeakThousandDataArray[i] = 1;
}
        j++;
      }
      else{
        FilteredRPeakThousandDataArray[i] = 0;
      }


     }

adiga · Accepted Answer · 2019-06-20 09:46:14Z

0

You can create an array with 0 for all 1500 indexes using fill. Thne loop through FilteredRPeakDataArray and update only those indexes which have value > j

var j = 500;
var FilteredRPeakDataArray = [2, 600, 800, 1200, 1300];
var FilteredRPeakThousandDataArray = Array(1500).fill(0);

FilteredRPeakDataArray.forEach(n => {
  if(n > j)
    FilteredRPeakThousandDataArray[n] = 1;
})

console.log(FilteredRPeakThousandDataArray[2]);
console.log(FilteredRPeakThousandDataArray[600]);
console.log(FilteredRPeakThousandDataArray[800]);

answered Jun 20, 2019 at 9:46

adiga

35.4k9 gold badges65 silver badges88 bronze badges

1 Comment

Code Maniac Over a year ago

it should be n >= j instead of n > j

wfreude · Accepted Answer · 2019-06-20 09:46:57Z

0

const start = 500;
const limit = 1500;
const FilteredRPeakDataArray = [2, 600, 800, 1200, 1300];
// fill array with 1s
const FilteredRPeakThousandDataArray = new Array(limit).fill(1);
// change value of indices stored in FilteredRPeakDataArray to 0
for (const idx of FilteredRPeakDataArray) {
   if (idx >= start) {
      FilteredRPeakThousandDataArray[idx] = 0;
   }
}
console.log("FilteredRPeakThousandDataArray " + FilteredRPeakThousandDataArray);

answered Jun 20, 2019 at 9:46

wfreude

5083 silver badges10 bronze badges

Comments

T.J. Crowder · Accepted Answer · 2019-06-20 09:47:22Z

I'd just pre-fill the array with 0 and then set 1 for those specific indexes:

var FilteredRPeakThousandDataArray = new Array(1500);
FilteredRPeakThousandDataArray.fill(0);
for (const index of FilteredRPeakDataArray) {
    if (index >= j) {
        FilteredRPeakThousandDataArray[index] = 1;
    }
}

Live Example:

var j = 500;
var FilteredRPeakDataArray = [2, 600, 800, 1200, 1300];
var FilteredRPeakThousandDataArray = new Array(1500);
FilteredRPeakThousandDataArray.fill(0);
for (const index of FilteredRPeakDataArray) {
    if (index >= j) {
        FilteredRPeakThousandDataArray[index] = 1;
    }
}

// Show results
for (const index of [0, ...FilteredRPeakDataArray]) {
    console.log(`FilteredRPeakThousandDataArray[${index}] = ${FilteredRPeakThousandDataArray[index]}`);
}

But if you want to set those values as you build the array, you can use Array.from's callback:

var FilteredRPeakThousandDataArray = Array.from({length: 1500}, (_, index) => {
    return index >= j && FilteredRPeakDataArray.includes(index) ? 1 : 0;
});

Live Example:

var j = 500;
var FilteredRPeakDataArray = [2, 600, 800, 1200, 1300];
var FilteredRPeakThousandDataArray = Array.from({length: 1500}, (_, index) => {
    return index >= j && FilteredRPeakDataArray.includes(index) ? 1 : 0;
});

// Show results
for (const index of [0, ...FilteredRPeakDataArray]) {
    console.log(`FilteredRPeakThousandDataArray[${index}] = ${FilteredRPeakThousandDataArray[index]}`);
}

Array#fill and Array.from are both relatively recent additions to JavaScript, but both can be polyfilled easily.

Code Maniac · Accepted Answer · 2019-06-20 09:47:47Z

0

You can compare j with i and then check for particular value inside FilteredRPeakDataArray array

var j = 500;
var FilteredRPeakDataArray = new Array();
var FilteredRPeakDataArray = [2, 600, 800, 1200, 1300];
var FilteredRPeakThousandDataArray = new Array(1500).fill(0);

for (var i = 0; i < 1500; i++) {
  if (i >= j && FilteredRPeakDataArray.includes(i)) {
    FilteredRPeakThousandDataArray[i] = 1;
  } else {
    FilteredRPeakThousandDataArray[i] = 0;
  }
}

console.log( FilteredRPeakThousandDataArray);

answered Jun 20, 2019 at 9:47

Code Maniac

37.9k5 gold badges44 silver badges65 bronze badges

Comments

Kobe · Accepted Answer · 2019-06-20 09:47:47Z

0

You could fill the 1500 element array with 0's from the start, filter the array to those element greater than j, and replace all indices with 1's:

var j = 500;

var FilteredRPeakDataArray = [2, 600, 800, 1200, 1300];

var FilteredRPeakThousandDataArray = new Array(1500).fill(0);

FilteredRPeakDataArray.filter(el => el > j).map(el => FilteredRPeakThousandDataArray[el] = 1)

console.log("FilteredRPeakThousandDataArray " + FilteredRPeakThousandDataArray);

answered Jun 20, 2019 at 9:47

Kobe

6,4681 gold badge18 silver badges38 bronze badges

Comments

saketh · Accepted Answer · 2019-06-20 10:11:50Z

0

first fill all the elements of array with 0 's and later change the required indexes to 1

var j = 500;
var FilteredRPeakDataArray = new Array();
var FilteredRPeakDataArray = [2, 600, 800, 1200, 1300];
var FilteredRPeakThousandDataArray = new Array(1500).fill(0);

for (var i = 0; i < FilteredRPeakDataArray.length; i++) {
    
  FilteredRPeakDataArray[i]>=j ? FilteredRPeakThousandDataArray[FilteredRPeakDataArray[i]]=1:null
  

}

console.log("FilteredRPeakThousandDataArray " + FilteredRPeakThousandDataArray);

edited Jun 20, 2019 at 10:11

answered Jun 20, 2019 at 9:46

saketh

8131 gold badge11 silver badges25 bronze badges

Collectives™ on Stack Overflow

Array filling in Javascript

8 Answers 8

Comments

Comments

1 Comment

Comments

Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

8 Answers 8

Comments

Comments

1 Comment

Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related