var TestString = '+'.repeat(200) + '='.repeat(20000) + '+'.repeat(200);

​

var regexTrim = function(str, ch) {

    if (ch === ']') ch = '\\]';

    else if (ch === '^') ch = '\\^';

    else if (ch === '\\') ch = '\\\\';

    return str.replace(new RegExp('^[' + ch + ']+|[' + ch + ']+$', 'g'), '');

};

​

function indexTrim(str, ch) {

    var start = 0, 

        end = str.length;

​

    while(start < end && str[start] === ch)

        ++start;

​

    while(end > start && str[end - 1] === ch)

        --end;

​

    return (start > 0 || end < str.length) ? str.substring(start, end) : str;

}

​

function booleanTrim(str, ch) {

    return str.split(ch).filter(Boolean).join(ch);

}

​

function spreadTrim(str, ch) {

    const first = [...str].findIndex(char => char !== ch);

    const last = [...str].reverse().findIndex(char => char !== ch);

    return str.substring(first, str.length - last);

}

​

function substringTrim(str, ch) {

    while(str.charAt(0)==ch) {

        str = str.substring(1);

    }

​

    while(str.charAt(str.length-1)==ch) {

        str = str.substring(0,str.length-1);

    }

​

    return str;

}