How to create an array of definable size with a repeating tail. JavaScript-CodePudding

It is necessary to create a function that would create an array with a repeating ending

I wrote such a function, but I understand that it is absolutely not optimal. Is it possible to solve the problem in another way?

const getArr = (arrayLength, patternLength, repeatedTailLength) => {
    const arr = Array.from(Array(patternLength), (_, index) => index  1 );
    const repeatedTailNumbers = arr.slice(patternLength - repeatedTailLength);
    const tailsCount = Math.floor((arrayLength - patternLength) / repeatedTailLength);
    const tailsOdd = arrayLength - (tailsCount * repeatedTailLength   patternLength);
    let result = [...arr];
    
    for(let i = 1; i <= tailsCount; i  ) {
      result = [...result, ...repeatedTailNumbers]
    }
     
    for(let i = 0; i < tailsOdd; i  ) {
      result.push(repeatedTailNumbers[i]);
    }
    
    return result;
}


console.log(getArr(27, 9, 4));

[
  1, 2, 3, 4, 5, 6, 7, 8, 9, 
  6, 7, 8, 9, 
  6, 7, 8, 9, 
  6, 7, 8, 9, 
  6, 7, 8, 9, 
  6, 7
]

CodePudding user response：

You could get the parts in advance and map the items.

const getArr = (arrayLength, patternLength, repeatedTailLength) => {
    const
        pattern = Array.from({ length: patternLength }, (_, i) => i   1),
        tail = pattern.slice(-repeatedTailLength);

    return Array.from(
        { length: arrayLength },
        (_, i) => i < pattern.length
            ? pattern[i]
            : tail[(i - pattern.length) % tail.length]
    );
}

console.log(...getArr(26, 9, 4));

CodePudding user response：

var tr = (count, last, times) => {
    let total = []
    for (let i = 1; i <= count; i  ) {
        if(total.length == count) return total
        if(i > last) i = i-times
        total.push(i)
    }
}
console.log(tr(26, 9, 4))