Java script flexible walk thru a string and return number of char-CodePudding

I have a task where I have to iterate thru a string and return a predefined number of chars in a row. So f.i. the string is "Thisisatest" and I have to start on the first position and return two characters. Have to proof them for som uniques (outside that scope) and if not proofed I have to shift the start be one and start on the second position and return two characters. Have to repeat this as long as I found a unique pair of chars or reached the end of the string.

So f.i. first loop: returns Th, then hi, is, si, is, sa, at...

Used this script:

function setInitials(Start,Num,Str){
    var initials=""
    if(Number(Start) Number(Num)-1 < Str.length){
        for (var i = Number(Start); i < Number(Num); i  ) {
            initials  = Str[i];
        }
    }
    return initials
}

where Start ist my Starting point, Num the Number of Chars to return ans Str the string.

But if I try setInitials("2","2","Thisiaatrest") I will get back nothing

CodePudding user response：

after more search I found the problem- the start end endpoint were the same. so the correct working function is:

function setInitials(Start,Num,Str){
    var initials=""
    var end = Number(Start) Number(Num)-1
    if(end-1 < Str.length){
        for (var i = Number(Start)-1; i < end; i  ) {
            initials  = Str[i];
        }
    }
    return initials
}

CodePudding user response：

You can check my solution.

function setInitials(start = 0, span = 0, str = '') {
    const [obj, tmp] = [{}, []];
    let [left, right, count] = [start, start, 0];

    while (right < str.length) {
        const char = str[right];
        if (!obj[char]) {
            obj[char] = 1;
            count  ;
        } else {
            obj[char]  ;
        }
        tmp.push(char);
        while (left < str.length && right - left   1 === span) {
            const _char = str[left];
            if (count === span) return tmp.join('');
            obj[_char] = Math.max(obj[_char] - 1, 0);
            if (obj[_char] === 0) count--;
            tmp.shift();
            left  ;
        }
        right  ;
    }

    return 'Not Found';
}

console.log(setInitials(0, 2, 'Thisisatest'));
console.log(setInitials(2, 2, 'Thisiaatrest'));
console.log(setInitials(0, 3, 'aaaabcaa'));
console.log(setInitials(0, 3, 'aaaaaaaa'));