如何在javascript中的对象中动态添加属性？

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);
} 

Answer 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]++;

Answer 2

这项工作

  typeof object[item] == 'undefined' ?

Answer 3

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);