Question 211828 in Javascript Question posted in
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Javascript – Fill a empty value of a key-value pair using the previous value

Fill a empty value of a key-value pair with the last value of the previous key.

myitems = {
 'items1': [{first:true, second:false}, {first:true, second:true}],
 'items2': [], //should be filled with {first:true, second:true}
 'items3': [], //should be filled with {first:true, second:true}
 'items4': [{first:true, second:false}, {first:true, second:true}],
 'items5': [{first:false, second:true}],
 'items6': [], //should be filled with {first:false, second:true}
 'items7': [{first:true, second:true}],
}
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2

Answers


  1. 0

    You can do something like this to achieve that.

    let lastValue = null;

for (const key in myitems) {
  if (myitems[key].length === 0) { // check if value array is empty or not
    // if yes, then
    // check if we have lastValue something, then set that into the current value of `key`
    if (lastValue !== null) {      
      myitems[key] = [lastValue];
    }
  } else {
    lastValue = myitems[key][myitems[key].length - 1];
    // `myitems[key][myitems[key].length - 1]` will give us the last entry in value array
    // we are storing this into our lastValue so that we could use it in future iterations, if we require
  }
}
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  2. 0 
    let myitems = {
  'items1': [{
    first: true,
    second: false
  }, {
    first: true,
    second: true
  }],
  'items2': [],
  'items3': [],
  'items4': [{
    first: true,
    second: false
  }, {
    first: true,
    second: true
  }],
  'items5': [{
    first: false,
    second: true
  }],
  'items6': [],
  'items7': [{
    first: true,
    second: true
  }],
};

let obj = {};
let previous;
for (let x in myitems) {
  if (myitems[x].length) {
    obj[x] = myitems[x];
    previous = myitems[x].slice(-1);
  } else {
    obj[x] = previous;
  }
}
console.log(JSON.parse(JSON.stringify(obj)));
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