sucrase/dist/src/NameManager.mjs

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

export default class NameManager {
    constructor(tokens) {
        this.tokens = tokens;
        this.usedNames = new Set();
    }
    preprocessNames() {
        for (const token of this.tokens.tokens) {
            if (token.type.label === "name") {
                this.usedNames.add(token.value);
            }
        }
    }
    claimFreeName(name) {
        const newName = this.findFreeName(name);
        this.usedNames.add(newName);
        return newName;
    }
    findFreeName(name) {
        if (!this.usedNames.has(name)) {
            return name;
        }
        let suffixNum = 2;
        while (this.usedNames.has(name + suffixNum)) {
            suffixNum++;
        }
        return name + suffixNum;
    }
}