A simple regular expression based lexer generator

LexGen.js

/**
 * @description A simple lexer generator in javascript
 */

class LexToken {
    constructor(name, value, index, row, col) {
        this.name = name;
        this.value = value;
        this.index = index;
        this.line = row;
        this.col = col;
    }
}

class LexerGenerator {
    constructor() {
        this.lexemes = {};
        this.buildReg = "";
        this.add = this.add.bind(this);
        this.build = this.build.bind(this);
    }

    add(label, grammar) {
        this.buildReg.length > 1 ? this.buildReg += `|${grammar}` : this.buildReg = grammar;
        return this;
    }

    build() {
        this.buildReg = new RegExp(this.buildReg, "g");
        return this;
    }

    lex(str) {
        return str.matchAll(this.buildReg);
    }
}

const lexerGen = new LexerGenerator();
lexerGen.add("IF", "if");
lexerGen.add("LBRACE", "\\(");
lexerGen.add("RBRACE", "\\)");
lexerGen.add("LCURL", "\\{");
lexerGen.add("RCURL", "\\}");
lexerGen.add("VAR", "var");
lexerGen.add("CONST", "const");
lexerGen.add("EQUAL", "=");
lexerGen.add("NAME", "\[a-zA-Z_\]\[a-zA-Z0-9_\]\+");
lexerGen.add("NUMBER", "\[0-9\]\+");
lexerGen.add("STRING", "\".\*\"");
lexerGen.add("SEMICOLON", ";");
lexerGen.add("PRINT", "print");

lex = lexerGen.build();
code = `{
var name = "d";
name = "Spiff Jekey-Green";
print(name);
}`;

const toks = lex.lex(code);
let t = null;
while(!(t = toks.next()).done) {
    console.log(t);
}