A simple js interview question

I saw some people asking questions in the js group, so I wrote a few questions with my hands-on mentality. Although the questions were not too difficult, they tested people's programming thinking. After reading others' answers, I found myself stupid. Put the code on. 1. If the result of adding 1 to the last element of an array is greater than 10, add 1 to the previous element and set the current element value to 0. The same applies to the previous element, for example, var a = new Array (); a [1] + 1; a = []; this question seems very simple, if the last element is equal to 10, add 1 to the money element and set the current element to 0. However, when all elements in the array are 9, add an element to the array. The answer is as follows: copy the code $ (function () {add () ;}) function add () {var a = [9, 4]; var B = a; var sum; B [B. length-1] = (B [B. length-1]) + 8; if (B [B. length-1]> = 10) {B [B. length-1] = B [B. length-1]-10; var I = B. length-2; while (I>-2) {if (I! =-1) {sum = B [I] + 1; if (sum> = 10) {B [I] = sum-10 ;} else {B [I] = sum; break;} I --;} else {a = [1];. push (B); I -- ;}}else {a = B;} alert (a) ;}copy the code and read the code written by others, I found myself complicated. I wrote a bunch of code. If I use the js unshift () function, it would be better to add one or more elements to the array header and return a new number length. Khan, I don't know much about my js. However, the essence of this writing is the same. I personally think the most correct writing method should be like this: copy the code // convert the integer and convert it into an array $. (function () {var num = [9, 9, 9, 9], intA = parseInt (num. join (","). replace (/,/gi, ""); intA ++; var newStr = intA. toString (), newArr = []; for (var I = 0, l = newStr. length; I <l; I ++) {newArr. push (parseInt (newStr [I]);} alert (newArr) ;}); Copying code is a matter of simulating decimal addition with arrays, therefore, converting to a number is the most direct and simple. At the same time, I also found a problem. Why is the gap between myself and others so big? There is also a query for the number of occurrences of each character in a string. For example, a s d f appears several times in 'assddfsds '. It was written but not saved, if you are not interested, you can check it yourself. Note that only JavaScript syntax is supported;