Function scanDelims

src/commonmark.js:1287–1342

(cc)

// they can open and/or close emphasis or strong emphasis.  A utility
// function for strong/emph parsing.
var scanDelims = function(cc) {
    var numdelims = 0;
    var char_before, char_after, cc_after;
    var startpos = this.pos;
    var left_flanking, right_flanking, can_open, can_close;
    var after_is_whitespace, after_is_punctuation, before_is_whitespace, before_is_punctuation;

    if (cc === C_SINGLEQUOTE || cc === C_DOUBLEQUOTE) {
        numdelims++;
        this.pos++;
    } else {
        while (this.peek() === cc) {
            numdelims++;
            this.pos++;
        }
    }

    if (numdelims === 0) {
        return null;
    }

    char_before = startpos === 0 ? '\n' : this.subject.charAt(startpos - 1);

    cc_after = this.peek();
    if (cc_after === -1) {
        char_after = '\n';
    } else {
        char_after = fromCodePoint(cc_after);
    }

    after_is_whitespace = reWhitespaceChar.test(char_after);
    after_is_punctuation = rePunctuation.test(char_after);
    before_is_whitespace = reWhitespaceChar.test(char_before);
    before_is_punctuation = rePunctuation.test(char_before);

    left_flanking = !after_is_whitespace &&
            !(after_is_punctuation && !before_is_whitespace && !before_is_punctuation);
    right_flanking = !before_is_whitespace &&
            !(before_is_punctuation && !after_is_whitespace && !after_is_punctuation);
    if (cc === C_UNDERSCORE) {
        can_open = left_flanking &&
            (!right_flanking || before_is_punctuation);
        can_close = right_flanking &&
            (!left_flanking || after_is_punctuation);
    } else if (cc === C_SINGLEQUOTE || cc === C_DOUBLEQUOTE) {
        can_open = left_flanking && !right_flanking;
        can_close = right_flanking;
    } else {
        can_open = left_flanking;
        can_close = right_flanking;
    }
    this.pos = startpos;
    return { numdelims: numdelims,
             can_open: can_open,
             can_close: can_close };
};

// Handle a delimiter marker for emphasis or a quote.