How to Replace Item in Array

How to replace item in array?

var index = items.indexOf(3452);

if (index !== -1) {
    items[index] = 1010;
}

Also it is recommend you not use the constructor method to initialize your arrays. Instead, use the literal syntax:

var items = [523, 3452, 334, 31, 5346];

You can also use the ~ operator if you are into terse JavaScript and want to shorten the -1 comparison:

var index = items.indexOf(3452);

if (~index) {
    items[index] = 1010;
}

Sometimes I even like to write a contains function to abstract this check and make it easier to understand what's going on. What's awesome is this works on arrays and strings both:

var contains = function (haystack, needle) {
    return !!~haystack.indexOf(needle);
};

// can be used like so now:
if (contains(items, 3452)) {
    // do something else...
}

Starting with ES6/ES2015 for strings, and proposed for ES2016 for arrays, you can more easily determine if a source contains another value:

if (haystack.includes(needle)) {
    // do your thing
}

How to replace or update item of array in JavaScript

You might have misused the slice method, change slice to splice works for me:

this.items.splice(index, 1, item)

slice doesn't trigger view updates according to the documentation here.

Vue wraps an observed array’s mutation methods so they will also
trigger view updates. The wrapped methods are:

• push()
• pop()
• shift()
• unshift()
• splice()
• sort()
• reverse()

Replacing objects in array

You can use Array#map with Array#find.

arr1.map(obj => arr2.find(o => o.id === obj.id) || obj);

var arr1 = [{    id: '124',    name: 'qqq'}, {    id: '589',    name: 'www'}, {    id: '45',    name: 'eee'}, {    id: '567',    name: 'rrr'}];
var arr2 = [{    id: '124',    name: 'ttt'}, {    id: '45',    name: 'yyy'}];
var res = arr1.map(obj => arr2.find(o => o.id === obj.id) || obj);
console.log(res);

Javascript: Efficiently replace Object in Array that has property with specified value in a stateful manner?

One trick I have used when performance is top priority is to store the data in an object with an array of numeric ids to keep track of everything.

Example similar to yours:

var arr = [
 { id: 1, text: 'aaa' },
 { id: 2, text: 'bbb' },
 { id: 3, text: 'ccc' },
 { id: 78, text: 'zzz' }
];

var lookup = arr.reduce((prev, next) => {
  prev[next.id] = next;
  prev.allIds.push(next.id);
  return prev;
}, { allIds: [] });

Now if you know the id you want to replace you don't need to loop at all

lookup[78] = { id: 78, text: 'new!' };

If you do want to loop through the array use the allIds property

lookup.allIds.forEach(x=> {
  let item = lookup[x];
  item.text = '';
});

Javascript - Replace multiple elements in an array using index

Use Array.fill()

var array1 = ['S', 'T', 'A', 'C', 'K', 'O', 'V', 'E', 'R', 'F', 'L', 'O', 'W'];

array1.fill('X', 3, 10)

console.log(array1)

How to replace specific values in array

Try

let array = [1,3,5];let def = {1: "Tree", 3:"Car", 5:"Dog"};
let r= array.map(x=>def[x]);
console.log(r);

How to replace values in an array based on table values?

You can create a mapping dictionary and then apply this mapping to your list. For example:

mapping = dict(table[1:])

out = [[mapping.get(v, v) for v in l] for l in a]
print(out)

Prints:

[[0.5, 0.5, 0.5], [0.5, 5, 0.05], [0.025, 0.005, 0.123]]

Replace items in array with elements from a different set

Code on Javascript:

let array1 = ['a', null, 'c', null, 'e']
let array2 = [1, 2, 3]

let output = []
let cursorPosition = 0; // cursorPosition is a pointer for `array2` index
let nullPositions = []

// find nullable positions; in our case here will be 1, 4
for (let i = 0; i < array1.length; i++) {
  if (array1[i] === null) {
    nullPositions.push(i)
  }
}

// find total expected numbers of arrays from given input and create that array
const totalArray = Math.pow(array2.length, nullPositions.length);
for (let i = 0; i < totalArray; i++) {
  output.push([...array1])
}

// replacement logic for the `null` values
for (let i = 0; i < nullPositions.length; i++) {
  cursorPosition = 0;
  // frequency: how often the cursor needs to change (depends on null position)
  let frequency = totalArray / Math.pow(array2.length, i + 1);
  let resetCursorPositionOn = frequency;
  for (let j = 0; j < output.length; j++) {
    if (j < resetCursorPositionOn) {
      output[j][nullPositions[i]] = array2[cursorPosition];
    } else {
      resetCursorPositionOn += frequency;
      cursorPosition++;
      if (cursorPosition === array2.length) {
        cursorPosition = 0;
      }
      output[j][nullPositions[i]] = array2[cursorPosition];
    }
  }
}
console.log(output);

Output:

[
  ["a",1,"c",1,"e"],
  ["a",1,"c",2,"e"],
  ["a",1,"c",3,"e"],
  ["a",2,"c",1,"e"],
  ["a",2,"c",2,"e"],
  ["a",2,"c",3,"e"],
  ["a",3,"c",1,"e"],
  ["a",3,"c",2,"e"],
  ["a",3,"c",3,"e"]
]

It works in any number of combinations.

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