Generate first n sequence of seeing and speaking numbers in JavaScript

Question

In mathematics, a "look-and-say" sequence is a sequence of integers that begins as follows -

1, 11, 21, 1211, 111221, 312211, …

For Once Upon a Time A member generates a member of a sequence, we read out the number of the previous member and count the number of numbers in the same number group.

For example, the next number to 1211 is -

111221

Because if we read the number 1211 out loud, it will be -

One one, one two, two one which gives us 111221

We need to write a JavaScript function, It accepts a number n and returns the first n items of the "look thelook and say" sequence.

Example

The following is the code-

Live demonstration

const num = 12;
const generateSequence = (num = 1) => {
   const lookAndSay = (val) => {
      let res = '';
      let chars = (val + ' ').split('');
      let last = chars[0];
      let count = 0;
      chars.forEach(c => {
         if(c === last){
            count++;
         }else{
            res += (count + '') + last;
            last = c;
            count = 1;
         };
      });
      return res;
   }
   let start = 1;
   const res = [];
   for(let i = 0; i < num; i++){
      res.push(String(start));
      start = lookAndSay(start);
   };
   return res;
};
console.log(generateSequence(num));

Output

The following is the console output-

[
   '1',
   '11',
   '21',
   '1211',
   '111221',
   '312211',
   '13112221',
   '1113213211',
   '31131211131221',
   '13211311123113112211',
   '11131221133112132113212221',
   '3113112221232112111312211312113211'
]

The above is the detailed content of Generate first n sequence of seeing and speaking numbers in JavaScript. For more information, please follow other related articles on the PHP Chinese website!