How do I compare string and boolean in Javascript?

I would just explicitly check for the string "true".

let data = value === "true";

Otherwise you could use JSON.parse() to convert it to a native JavaScript value, but it's a lot of overhead if you know it's only the strings "true" or "false" you will receive.

var data = true;
data === "true" //false
String(data) === "true" //true

This works fine.

Try expression data == "true"

Tests:

data = "false" -- value will be false

date = "true" -- value will be true

Also, fix your JSON. JSON can handle booleans just fine.

• If one of the operands is a boolean, convert the boolean operand to 1 if it is true and +0 if it is false.
• When comparing a number to a string, try to convert the string to a numeric value.

from MDN Equality Operators page

Examples:

true == "true";   // 1 == NaN → false
true == "1";      // 1 == 1   → true
false == "false"; // 0 == NaN → false
false == "";      // 0 == 0   → true
false == "0";     // 0 == 0   → true