How to add properties dynamically in the object in javascript?

Question

I want to know that how many times each alphabet comes in the 'input' variable. For this I am loop through each character and storing them in an object and also how many they appeared in the sentence. But It is consoling NaN. Please show me where is the error?

var input = "why this kolaveri kolaveri di";
function processData(input) {
    var object = {};
    input.replace(/\s/g,"").split("").forEach(function(item){
        object[item] == 'undefined' ? object[item] = 0 && object[item]++ : object[item]++ ;
    });
    console.log(object);
}

For starters, object[item] == 'undefined' needs to be object[item] == undefined with no quotes around undefined and it would be even better to use object[item] === undefined with the === so there's no type conversion going on. Though, I personally would use object.hasOwnProperty(item) myself. — jfriend00
– jfriend00, Commented Oct 3, 2015 at 16:57

GolezTrol · Accepted Answer · 2015-10-03 16:54:18Z

1

You can use hasOwnProperty to check if a property exists.

var input = "why this kolaveri kolaveri di";


var object = {};
input.replace(/\s/g,"").split("").forEach(function(item){
  
  // If the property doesn't exist, initialize it to 0
  if (!object.hasOwnProperty(item))
    object[item] = 0;
  
  object[item]++
});
console.log(object);

For the haters, you can initialize to 1 and only increment in the else. Essentially the same but a few cycles more efficient. Use whichever you think looks best.

  // If the property doesn't exist, initialize it to 1
  if (!object.hasOwnProperty(item))
    object[item] = 1;
  else
    object[item]++;

answered Oct 3, 2015 at 16:54

GolezTrol

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Artemiy StagnantIce Alexeew · Accepted Answer · 2015-10-03 17:02:11Z

0

This work

  typeof object[item] == 'undefined' ?

answered Oct 3, 2015 at 17:02

Artemiy StagnantIce Alexeew

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Kishore Sahasranaman · Accepted Answer · 2015-10-03 17:03:43Z

0

You had the problem in the below line of code .

object[item] == 'undefined' ? object[item] = 0 && object[item]++ : object[item]++ ;

Update Code:

var input = "why this kolaveri kolaveri di";
function processData(input) {
    var object = {};
    input.replace(/\s/g,"").split("").forEach(function(item){
        if(object[item] == null)
        { 
            object[item] = 0;
            object[item]++; 
        }else{
            object[item]++;
        }
    });
    console.log(object);
}

//testing here 
processData(input);

answered Oct 3, 2015 at 17:03

Kishore Sahasranaman

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