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tokenizer.js

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const WHITESPACE = [" ", "\n", "\t"];

function getOpenTagName(htmlString, pos) {

let tagName = "";

let char = htmlString.charAt(pos);

while (char !== ">" && char !== " " && char !== "/" && char !== "") {

tagName += char;

char = htmlString.charAt(++pos);

}

return tagName;

}

function getCloseTagName(htmlString, pos) {

let tagName = "";

let char = htmlString.charAt(pos);

while (char !== ">" && char !== "") {

tagName += char;

char = htmlString.charAt(++pos);

}

return tagName;

}

function getWhiteSpace(htmlString, pos) {

let whitespace = "";

let char = htmlString.charAt(pos);

while (WHITESPACE.includes(char) && char !== "") {

whitespace += char;

char = htmlString.charAt(++pos);

}

return whitespace;

}

function getAttributeName(htmlString, pos) {

let attributeName = "";

let char = htmlString.charAt(pos);

while (char !== "=" && char !== " " && char !== ">" && char !== "") {

attributeName += char;

char = htmlString.charAt(++pos);

}

return attributeName;

}

function getAttributeValue(htmlString, pos, quote) {

let attributeValue = "";

let char = htmlString.charAt(pos);

const isAtEnd = (c) => {

if (quote) {

return c === quote || c === "";

}

return c === " " || c === ">" || c === "/" || c === "";

};

while (!isAtEnd(char)) {

attributeValue += char;

char = htmlString.charAt(++pos);

}

return attributeValue;

}

function getText(htmlString, pos) {

let text = "";

let char = htmlString.charAt(pos);

while (char !== "<" && char !== "") {

text += char;

char = htmlString.charAt(++pos);

}

return text;

}

export function tokenizeHTML(htmlString) {

let pos = 0;

let isInTag = false;

let isInAttribute = false;

let isAfterAttributeEqual = false;

const tokens = [];

while (pos < htmlString.length) {

const char = htmlString.charAt(pos);

const nextChar = htmlString.charAt(pos + 1);

if (char === "<" && nextChar !== "/" && !isInTag && !isInAttribute) {

isInTag = true;

tokens.push({ type: "openTagStart", value: "<", pos });

pos++;

const tagName = getOpenTagName(htmlString, pos);

tokens.push({ type: "tagName", value: tagName, pos });

pos += tagName.length;

continue;

}

if (WHITESPACE.includes(char) && isInTag) {

const whitespace = getWhiteSpace(htmlString, pos);

tokens.push({ type: "whitespace", value: whitespace, pos });

pos += whitespace.length;

isInAttribute = false;

continue;

}

if (char === ">" && isInTag && !isInAttribute) {

isInTag = false;

tokens.push({ type: "openTagEnd", value: ">", pos });

pos++;

continue;

}

if (isInTag && !isInAttribute && char === "/" && nextChar === ">") {

isInTag = false;

tokens.push({ type: "selfClose", value: "/>", pos });

pos += 2;

continue;

}

if (isInTag && !isInAttribute) {

isInAttribute = true;

const attributeName = getAttributeName(htmlString, pos);

tokens.push({ type: "attributeName", value: attributeName, pos });

pos += attributeName.length;

if (htmlString.charAt(pos) !== "=" && htmlString.charAt(pos) !== "'" && htmlString.charAt(pos) !== '"') {

isInAttribute = false;

}

continue;

}

if (char === "=" && isInAttribute && isInTag) {

isAfterAttributeEqual = true;

tokens.push({ type: "equal", value: "=", pos });

pos++;

continue;

}

if (isAfterAttributeEqual && isInAttribute && isInTag) {

const hasQuote = char === "'" || char === '"';

const quote = hasQuote ? char : "";

if (hasQuote) {

tokens.push({ type: "quoteStart", value: quote, pos });

pos++;

}

const attributeValue = getAttributeValue(htmlString, pos, quote);

tokens.push({ type: "attributeValue", value: attributeValue, pos });

pos += attributeValue.length;

if (hasQuote && htmlString.charAt(pos) === quote) {

tokens.push({ type: "quoteEnd", value: quote, pos });

pos++;

}

isInAttribute = false;

isAfterAttributeEqual = false;

continue;

}

if (!isInTag && char === "<" && nextChar === "/") {

tokens.push({ type: "closeTagStart", value: "</", pos });

pos += 2;

const tagName = getCloseTagName(htmlString, pos);

tokens.push({ type: "tagName", value: tagName, pos });

pos += tagName.length;

if (htmlString.charAt(pos) === ">") {

tokens.push({ type: "closeTagEnd", value: ">", pos });

pos++;

}

continue;

}

if (!isInTag) {

const text = getText(htmlString, pos);

tokens.push({ type: "text", value: text, pos });

pos += text.length;

continue;

}

}

return tokens;

}