sucrase/dist/src/TokenProcessor.mjs

Super-fast alternative to Babel for when you can target modern JS runtimes

export default class TokenProcessor {
    constructor(code, tokens) {
        this.code = code;
        this.tokens = tokens;
        this.resultCode = '';
        this.tokenIndex = 0;
    }
    reset() {
        this.resultCode = '';
        this.tokenIndex = 0;
    }
    matchesAtIndex(index, tagLabels) {
        if (index < 0) {
            return false;
        }
        for (let i = 0; i < tagLabels.length; i++) {
            if (index + i >= this.tokens.length) {
                return false;
            }
            if (this.tokens[index + i].type.label !== tagLabels[i]) {
                return false;
            }
        }
        return true;
    }
    matchesNameAtIndex(index, name) {
        return this.matchesAtIndex(index, ['name']) && this.tokens[index].value === name;
    }
    matches(tagLabels) {
        return this.matchesAtIndex(this.tokenIndex, tagLabels);
    }
    matchesName(name) {
        return this.matchesNameAtIndex(this.tokenIndex, name);
    }
    previousWhitespace() {
        return this.code.slice(this.tokenIndex > 0
            ? this.tokens[this.tokenIndex - 1].end
            : 0, this.tokens[this.tokenIndex].start);
    }
    replaceToken(newCode) {
        this.resultCode += this.previousWhitespace();
        this.resultCode += newCode;
        this.tokenIndex++;
    }
    replaceTokenTrimmingLeftWhitespace(newCode) {
        this.resultCode += this.previousWhitespace().replace(/[\t ]/g, '');
        this.resultCode += newCode;
        this.tokenIndex++;
    }
    removeInitialToken() {
        this.replaceToken('');
    }
    removeToken() {
        this.replaceTokenTrimmingLeftWhitespace('');
    }
    copyExpectedToken(label) {
        if (this.tokens[this.tokenIndex].type.label !== label) {
            throw new Error(`Expected token ${label}`);
        }
        this.copyToken();
    }
    copyToken() {
        this.resultCode += this.code.slice(this.tokenIndex > 0
            ? this.tokens[this.tokenIndex - 1].end
            : 0, this.tokens[this.tokenIndex].end);
        this.tokenIndex++;
    }
    appendCode(code) {
        this.resultCode += code;
    }
    currentToken() {
        return this.tokens[this.tokenIndex];
    }
    currentIndex() {
        return this.tokenIndex;
    }
    finish() {
        if (this.tokenIndex !== this.tokens.length) {
            throw new Error('Tried to finish processing tokens before reaching the end.');
        }
        this.resultCode += this.code.slice(this.tokens[this.tokens.length - 1].end);
        return this.resultCode;
    }
    isAtEnd() {
        return this.tokenIndex === this.tokens.length;
    }
}