JS util functions

function isArray(ob) {
// return ob.constructor == Array;
var ret = false;
try {
ret = ob.length !== undefined;
}
catch(e) {
ret = false;
}
return ret;
}
function isObject(ob) {
return typeof ob == "object";
}
function isFunction(ob) {
return typeof ob == "function";
}
function isString(ob) {
return typeof ob == "string";
}
function isNumber(ob) {
return typeof ob == "number";
}