CODEWITHSUNDEEP
javascriptjsonkey
Stephen Hoydis
Stephen Hoydis

Reputation: 39

JAVASCRIPT: pass json key's name as parameter, and use the parameter to get the value

In javascript, is there a way to treat a JSON keyname as a variable?

For instance, below I want to perform (any set of actions) on the value of a different key in JSON each time, by telling it which json key to get by feeding the keyname to the function as a parameter.

The basic idea here is: Make a function to do (x) no matter what JSON it's given. I just need to tell it what key I want.

var myObj = {name: "John", age: 31}; // dataset #1
var myObj2 = {month: "January", day: 20}; //dataset #2

function myFunction(jsonName, variableKeyName) {   

  var variableKeyValue = jsonName + "." + variableKeyName;  //wrong way to do this, apparently.
 
  console.log(variableKeyValue); 
}

myFunction("myObj", "name"); //want this to log "John", not the string "myObj.name".
myFunction("myObj2", "day"); //want this to log "20", not the string "myObj2.day".

Is this possible? How do get the function to assign the VALUE of the string I'm building with the parameter, rather than just the string as "jsonNameX.variableKeyNameX"?

Upvotes: 2

Views: 2341

Answers (2)

Thunderarea
Thunderarea

Reputation: 479

Yes you can do it. You can get the JSON value like this:

jsonName.variableKeyName;

but you can also get it like this:

jsonName["variableKeyName"];

(https://www.w3schools.com/js/js_json_syntax.asp)

So you can change your code in this way:

var myObj = {name: "John", age: 31}; // dataset #1
var myObj2 = {month: "January", day: 20}; //dataset #2

function myFunction(jsonName, variableKeyName) {  
  var variableKeyValue = jsonName[variableKeyName];
  console.log(variableKeyValue ); 
}

myFunction(myObj, "name"); //this prints "John"
myFunction(myObj2, "day"); //this prints "20"

Upvotes: 1

Marco Mazzone
Marco Mazzone

Reputation: 79

const myObj = {name: "John", age: 31}; // dataset #1
const myObj2 = {month: "January", day: 20}; //dataset #2

function myFunction(json, variableKeyName) {   
  const variableKeyValue = json[variableKeyName]; 
  console.log(variableKeyValue); 
}

myFunction(myObj, "name"); // this log "John"
myFunction(myObj2, "day"); // this log 20

or you can access to global context using "this" keyword and variable name (instead variable identifier == reference)

const myObj = {name: "John", age: 31}; // dataset #1
const myObj2 = {month: "January", day: 20}; //dataset #2

function myFunction(jsonName, variableKeyName) {   
  const variableKeyValue = this[jsonName][variableKeyName]; 
  console.log(variableKeyValue); 
}

myFunction("myObj", "name"); // this log "John"
myFunction("myObj2", "day"); // this log 20

Upvotes: 2

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