currying function instead of if condition in javascript

By using Church_Booleans, you could use the following functions.

const
    TRUE = a => b => a,
    FALSE = a => b => b,
    IF = p => a => b => p(a)(b);

console.log(IF(TRUE)('1')('2'));  // 1
console.log(IF(FALSE)('1')('2')); // 2

Here's a way to implement True, False, and If without using any control flow statements like if...else or switch..case, control flow expressions like ?:, or higher-order functions.

const True  = 1;
const False = 0;

const If = Bool => Then => Else => [Else, Then][Bool];

console.log(If(True)('1')('2'));  // 1
console.log(If(False)('1')('2')); // 2

This is a defunctionalization of the Church encoding solution. Hence, it's more efficient.