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javascriptstring-concatenation

Javascript Concatenate Strings based on conditions

Is there a good way to accomplish this Javascript?

Basically I want something where the values of the fields are concatenate into a single field with comma between the values. Figure something simple like this

var a
var b
var c

allfieldvalue = a + ","b + ","c

My issue is I need to build condition in order for them to be put into allfieldvalue. So if var a = true, var b = false, and var c = true, then allfieldvalue = a +","c. Keep in mind, there could 20 different var. Hopefully that makes sense.

Solution

  • In case the goal is a string containing the names of variables that are true, use this approach:

    Make the variables into object props...

    var a = true;
var b = false;
var c = true;

let object = { a, b, c };  // produces { a: true, b: false, c: true }

    Filter that object to exclude false values:

    object = Object.fromEntries(
  Object.entries(object).filter(([k,v]) => v) // produces { a: true, c: true }
)

    Concat the keys:

    let string = Object.keys(object).join(',');  // produces "a,c"

    Demo

    var a = true;
var b = false;
var c = true;

let object = { a, b, c }; 

object = Object.fromEntries(
  Object.entries(object).filter(([k,v]) => v) 
)

let string = Object.keys(object).join(','); 
console.log(string)