node.js数据类型检查

export function isString(arg) {

return arg && typeof(arg) == "string";

}

export function isNumber(arg) {

return arg && typeof(arg) == "number" && !isNaN(arg);

}

export function isBoolean(arg) {

return arg === !!arg;

}

export function isArray(arg) {

return Object.prototype.toString.call(arg) == '[object Array]';

}

export function isObject(arg) {

return Object.prototype.toString.call(arg) == '[object Object]';

}

export function isFunction(arg) {

return Object.prototype.toString.call(arg) == '[object Function]';

}

export function isEmpty(arg) {

return Object.keys(arg).length === 0;

}