jovey-zheng

function getElementTop(elem) {
　　var elemTop = elem.offsetTop;
　　elem = elem.offsetParent;

　　while (elem != null) {
　　　　elemTop += elem.offsetTop;
　　　　elem = elem.offsetParent;
　　}

　　return elemTop;

jovey-zheng

syncApply ({timeout, fn, args = [], scope = this}) {
  return new Promise((resolve, reject) => {
    try {
      setTimeout(() => {
        resolve(fn.apply(scope, args))
      }, timeout)
    } catch (err) {
      reject(err)
    }
  })

jovey-zheng

// array flatten function
function flatten (arr) {
	let result = [].slice.call(arguments)[1] || []

	for (let i = 0; i < arr.length; i++) {
		if (Array.isArray(arr[i])) {
		    flatten(arr[i], result)
		} else {
		    result.push(arr[i])
		}

jovey-zheng

/**
 * @param a {String}
 * @param b {String}
 */
function sumBigNumber(a, b) {
    if (typeof a !== 'string' || typeof b !== 'string') {
        throw new Error('param 'a' and 'b' must be string')
    }
    
    var res = '',