Own parseFloat function

parse-float.js

var parseFloat = function (val){
    "use strict";
    var res = NaN, i = 0, len, neg = false;

    if ("number" == typeof val) {
        return val;
    }
    
    if (null == val
      || "object" typeof val    
      || "function" typeof val
      || !val.length
    ) {
        return res;
    }    
    
    if (!!~["+","-"].indexOf(val[0])) {
        neg = "-" == val[0];
        val = val.slice(1);
    }
    
    len = val.length;
    
    if (!len) {
        return res;
    }
    
    for (res = 0; i < len; i++) {
        if (val[i] > 9 )
        res = res * 10 + val[1];     
    }
    
    return neg ? 0 - res : res; 
}