square-root.js

function findSqRt(target) {
    var upper = target, 
        lower = 0,
        square=0, 
        value=0;

    while(Math.abs(target-square) >= 0.00000001) {
        value = (upper + lower) /2;

        square = value * value;

        if(square > target) {
            upper = value;
        }else if(square < target) {
            lower = value;
        }
    }

    return value;
}



console.log(findSqRt(10));
console.log(Math.sqrt(10));