heron.js

function round(num) {    
    return +(Math.round(num + "e+10")  + "e-10");
}

function heron_sqrt(num) {

    let a = num / 3

    let b = num / a

    while (round(Math.pow(a, 2)) !== num) {

        a = (a + b) / 2
        b = num / a

    }
    
    return a

}