Lazy evaluation for synchronous JS function, 'memoization'

sync-lazy.js

// synchronous lazy eval

// ES6
// function lazy (ev) { return x => this.cache = this.cache || ev(x) }

function Lazy(ev) {
    return function (x) {
        return this.cache = this.cache || ev(x)
    }.bind(this)
}


function slow (n) {
    var s = process.uptime()
    while(process.uptime() < s + 2);
    return 2*n
}

var a = new Lazy(slow)

// takes two seconds
var b = a(3)
console.log(b)

// instant, returned from cache
var b2 = a(3)
console.log(b2)