Alex1990

/**
 * Author: Alex Chao(alexchao1990@gmail.com)
 * Date: 2014-08-01
 */

/**
 * Note: You can choose the other polyfill which is compatible with ECMA-262, 5th edition
 * Url: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map
 */

Alex1990

/**
 * Author: Alex Chao(alexchao1990@gmail.com)
 * Date: 2014-08-02
 */

/**
 * Note: You can choose the other polyfill which is compatible with ECMA-262, 5th edition
 * Url: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach
 */

Alex1990

// Check if a string consists of the digit characters (0-9)
function isDigit(str) {
    return str && !/[^\d]/.test(str);
}

Alex1990

/*
 * Ref: http://stackoverflow.com/questions/1353684/detecting-an-invalid-date-date-instance-in-javascript
 */

function isValidDate(d) {
    return Object.prototype.toString.call(d) === '[object Date]' && !isNaN(d.valueOf());
}

Alex1990

/*
 * Ref: http://stackoverflow.com/questions/154059/how-do-you-check-for-an-empty-string-in-javascript
 */

// `str` must be a string
function isEmpty(str) {
    return !!str.length;
}

// check if the `str` is empty, null or undefined (`str` may be 0 or false)

Alex1990

/*
 * Ref: http://stackoverflow.com/questions/154059/how-do-you-check-for-an-empty-string-in-javascript
 */
function isBlank(str) {
    return !str || !/\S/.test(str);
}

Alex1990

// when you need a range, you'd better use comparison operators
function isFullYear(year) {
    return !/^\d{4}$/.test(year);
}

Alex1990

/**
 * Description: Count a string (mixing English and Chinese characters) length. 
 *      A basic and rough function.
 * 
 * Performance:
 *      Multiple methods performance test on http://jsperf.com/count-string-length.
 *      You can see that using regexp to check range is very slow from the above test page.
 */
function strLen(str) {
    var count = 0;

Alex1990

// Check if a value is falsy. This is, its value is one of undefined, null, false, 0, NaN or an empty string "".
// Also, you can use the Boolean function to convert the value.
function isFalsy(o) {
    return !o;
}

Alex1990

// Check if a value is truthy. The word truthy means the value is not one of undefined, null, false, 0, NaN or an empty string "".
// Also, you can use the Boolean function to convert the value.
function isTruthy(o) {
    return !!o;
}