Replacing values in JSON object

Question

I have the following JSON object data returned from my apicontroller :

[  
  {"id":2,"text":"PROGRAMME","parent":null},
  {"id":3,"text":"STAGE","parent":2},
  {"id":4,"text":"INFRA","parent":2},
  {"id":5,"text":"SYSTEM","parent":3},
  {"id":6,"text":"STOCK","parent":3}, 
  {"id":7,"text":"DPT","parent":3},
  {"id":9,"text":"EXTERNAL","parent":null} 
]

I want to replace "parent":null with "parent":'"#"'

I have tried the code below, but it is only replacing the first occurrence of "parent":null. How can I replace all "parent":null entries?

$(document).ready(function () {
    $.ajax({
        url: "http://localhost:37994/api/EPStructures2/",
        type: "Get",
        success: function (data) {
            var old = JSON.stringify(data).replace(null, "'#'"); //convert to JSON string
            var new = JSON.parse(old); //convert back to array
        },
        error: function (msg) { alert(msg); }
    });
});

Thanks,

Solution 1

You need to make the replace global:

var old = JSON.stringify(data).replace(/null/g, '"#"'); //convert to JSON string
var newArray = JSON.parse(old); //convert back to array

This way it will continue to replace nulls until it reaches the end

Regex docs:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp

Also, as a side note, you should avoid using new as a variable name as it is a reserved word in javascript and most browsers will not allow you to use it

Solution 2

@JonathanCrowe's answer is correct for regex, but is that the right choice here? Particularly if you have many items, you'd be much better off modifying the parsed object, rather than running it through JSON.stringify for a regex solution:

data.forEach(function(record) {
    if (record.parent === null) {
        record.parent = "#";
    }
});

In addition to being faster, this won't accidentally replace other nulls you want to keep, or mess up a record like { text: "Denullification Program"}.

Comments

[Jonathan Crowe]

Totally agree with this, if you are only looking to replace null "parent" keys then you are certainly better off with this approach to avoid any unwanted side effects

[jerome]

So obvious, although I was having trouble with this on my own. Thanks!