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Merged
merged 2 commits into from
Oct 3, 2020
Merged

replace string slices with startsWith comparison #9

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ec66888
replace string slices with startsWith comparison
JoostK Oct 2, 2020
3de3687
Apply suggestions from code review
guybedford Oct 3, 2020
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replace string slices with startsWith comparison
  • Loading branch information
@JoostK
JoostK committed Oct 2, 2020
commit ec668887ec4a49349a3b5d436065596a15c6b58d
80 changes: 40 additions & 40 deletions lexer.js
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Original file line number Diff line number Diff line change
Expand Up @@ -79,7 +79,7 @@ function parseSource (cjsSource) {
if (openTokenDepth === 0) {
switch (ch) {
case 105/*i*/:
if (source.slice(pos + 1, pos + 6) === 'mport' && keywordStart(pos))
if (source.startsWith('mport', pos + 1) && keywordStart(pos))
throwIfImportStatement();
lastTokenPos = pos;
continue;
Expand All @@ -90,9 +90,9 @@ function parseSource (cjsSource) {
lastTokenPos = pos;
continue;
case 95/*_*/:
if (source.slice(pos + 1, pos + 8) === '_export' && (keywordStart(pos) || source.charCodeAt(pos - 1) === 46/*.*/)) {
if (source.startsWith('_export', pos + 1) && (keywordStart(pos) || source.charCodeAt(pos - 1) === 46/*.*/)) {
pos += 8;
if (source.slice(pos, pos + 4) === 'Star')
if (source.startsWith('Star', pos))
pos += 4;
if (source.charCodeAt(pos) === 40/*(*/) {
openTokenPosStack[openTokenDepth++] = lastTokenPos;
Expand All @@ -107,23 +107,23 @@ function parseSource (cjsSource) {

switch (ch) {
case 101/*e*/:
if (source.slice(pos + 1, pos + 6) === 'xport' && keywordStart(pos)) {
if (source.startsWith('xport', pos + 1) && keywordStart(pos)) {
if (source.charCodeAt(pos + 6) === 115/*s*/)
tryParseExportsDotAssign(false);
else if (openTokenDepth === 0)
throwIfExportStatement();
}
break;
case 99/*c*/:
if (keywordStart(pos) && source.slice(pos + 1, pos + 5) === 'lass' && isBrOrWs(source.charCodeAt(pos + 5)))
if (keywordStart(pos) && source.startsWith('lass', pos + 1) && isBrOrWs(source.charCodeAt(pos + 5)))
nextBraceIsClass = true;
break;
case 109/*m*/:
if (source.slice(pos + 1, pos + 6) === 'odule' && keywordStart(pos))
if (source.startsWith('odule', pos + 1) && keywordStart(pos))
tryParseModuleExportsDotAssign();
break;
case 79/*O*/:
if (source.slice(pos + 1, pos + 6) === 'bject' && keywordStart(pos))
if (source.startsWith('bject', pos + 1) && keywordStart(pos))
tryParseObjectDefineOrKeys(openTokenDepth === 0);
break;
case 40/*(*/:
Expand Down Expand Up @@ -233,11 +233,11 @@ function tryBacktrackAddStarExportBinding (bPos) {
bPos--;
switch (source.charCodeAt(bPos)) {
case 114/*r*/:
if (source.slice(bPos - 2, bPos) !== 'va')
if (!source.startsWith('va', bPos - 2))
return;
break;
case 116/*t*/:
if (source.slice(bPos - 2, bPos) !== 'le' && source.slice(bPos - 4, bPos) !== 'cons')
if (!source.startsWith('le', bPos - 2) && !source.startsWith('cons', bPos - 4))
return;
break;
default: return;
Expand All @@ -254,7 +254,7 @@ function tryParseObjectDefineOrKeys (keys) {
if (ch === 46/*.*/) {
pos++;
ch = commentWhitespace();
if (ch === 100/*d*/ && source.slice(pos + 1, pos + 14) === 'efineProperty') {
if (ch === 100/*d*/ && source.startsWith('efineProperty', pos + 1)) {
pos += 14;
revertPos = pos - 1;
ch = commentWhitespace();
Expand All @@ -279,7 +279,7 @@ function tryParseObjectDefineOrKeys (keys) {
}
}
}
else if (keys && ch === 107/*k*/ && source.slice(pos + 1, pos + 4) === 'eys') {
else if (keys && ch === 107/*k*/ && source.startsWith('eys', pos + 1)) {
while (true) {
pos += 4;
revertPos = pos - 1;
Expand All @@ -298,14 +298,14 @@ function tryParseObjectDefineOrKeys (keys) {
if (ch !== 46/*.*/) break;
pos++;
ch = commentWhitespace();
if (ch !== 102/*f*/ || source.slice(pos + 1, pos + 7) !== 'orEach') break;
if (ch !== 102/*f*/ || !source.startsWith('orEach', pos + 1)) break;
pos += 7;
ch = commentWhitespace();
revertPos = pos - 1;
if (ch !== 40/*(*/) break;
pos++;
ch = commentWhitespace();
if (ch !== 102/*f*/ || source.slice(pos + 1, pos + 8) !== 'unction') break;
if (ch !== 102/*f*/ || !source.startsWith('unction', pos + 1)) break;
pos += 8;
ch = commentWhitespace();
if (ch !== 40/*(*/) break;
Expand All @@ -321,23 +321,23 @@ function tryParseObjectDefineOrKeys (keys) {
if (ch !== 123/*{*/) break;
pos++;
ch = commentWhitespace();
if (ch !== 105/*i*/ || source.slice(pos + 1, pos + 3) !== 'f ') break;
if (ch !== 105/*i*/ || !source.startsWith('f ', pos + 1)) break;
pos += 3;
ch = commentWhitespace();
if (ch !== 40/*(*/) break;
pos++;
ch = commentWhitespace();
if (it_id !== source.slice(pos, pos + it_id.length)) break;
if (!source.startsWith(it_id, pos)) break;
pos += it_id.length;
ch = commentWhitespace();
// `if (` IDENTIFIER$2 `===` ( `'default'` | `"default"` ) `||` IDENTIFIER$2 `===` ( '__esModule' | `"__esModule"` ) `) return` `;`? |
if (ch === 61/*=*/) {
if (source.slice(pos + 1, pos + 3) !== '==') break;
if (!source.startsWith('==', pos + 1)) break;
pos += 3;
ch = commentWhitespace();
if (ch !== 34/*"*/ && ch !== 39/*'*/) break;
let quot = ch;
if (source.slice(pos + 1, pos + 8) !== 'default') break;
if (!source.startsWith('default', pos + 1)) break;
pos += 8;
ch = commentWhitespace();
if (ch !== quot) break;
Expand All @@ -354,7 +354,7 @@ function tryParseObjectDefineOrKeys (keys) {
ch = commentWhitespace();
if (ch !== 34/*"*/ && ch !== 39/*'*/) break;
quot = ch;
if (source.slice(pos + 1, pos + 11) !== '__esModule') break;
if (!source.startsWith('__esModule', pos + 1)) break;
pos += 11;
ch = commentWhitespace();
if (ch !== quot) break;
Expand All @@ -363,7 +363,7 @@ function tryParseObjectDefineOrKeys (keys) {
if (ch !== 41/*)*/) break;
pos += 1;
ch = commentWhitespace();
if (ch !== 114/*r*/ || source.slice(pos + 1, pos + 6) !== 'eturn') break;
if (ch !== 114/*r*/ || !source.startsWith('eturn', pos + 1)) break;
pos += 6;
ch = commentWhitespace();
if (ch === 59/*;*/)
Expand All @@ -372,12 +372,12 @@ function tryParseObjectDefineOrKeys (keys) {
}
// `if (` IDENTIFIER$2 `!==` ( `'default'` | `"default"` ) `)`
else if (ch === 33/*!*/) {
if (source.slice(pos + 1, pos + 3) !== '==') break;
if (!source.startsWith('==', pos + 1, pos + 3)) break;
pos += 3;
ch = commentWhitespace();
if (ch !== 34/*"*/ && ch !== 39/*'*/) break;
const quot = ch;
if (source.slice(pos + 1, pos + 8) !== 'default') break;
if (!source.startsWith('default', pos + 1, pos + 8)) break;
pos += 8;
ch = commentWhitespace();
if (ch !== quot) break;
Expand Down Expand Up @@ -429,7 +429,7 @@ function tryParseObjectDefineOrKeys (keys) {
if (ch !== 46/*.*/) break;
pos++;
ch = commentWhitespace();
if (ch !== 100/*d*/ || source.slice(pos + 1, pos + 14) !== 'efineProperty') break;
if (ch !== 100/*d*/ || !source.startsWith('efineProperty', pos + 1)) break;
pos += 14;
ch = commentWhitespace();
if (ch !== 40/*(*/) break;
Expand All @@ -440,7 +440,7 @@ function tryParseObjectDefineOrKeys (keys) {
if (ch !== 44/*,*/) break;
pos++;
ch = commentWhitespace();
if (source.slice(pos, pos + it_id.length) !== it_id) break;
if (!source.startsWith(it_id, pos)) break;
pos += it_id.length;
ch = commentWhitespace();
if (ch !== 44/*,*/) break;
Expand All @@ -449,25 +449,25 @@ function tryParseObjectDefineOrKeys (keys) {
if (ch !== 123/*{*/) break;
pos++;
ch = commentWhitespace();
if (ch !== 101/*e*/ || source.slice(pos + 1, pos + 10) !== 'numerable') break;
if (ch !== 101/*e*/ || !source.startsWith('numerable', pos + 1)) break;
pos += 10;
ch = commentWhitespace();
if (ch !== 58/*:*/) break;
pos++;
ch = commentWhitespace();
if (ch !== 116/*t*/ && source.slice(pos + 1, pos + 4) !== 'rue') break;
if (ch !== 116/*t*/ && !source.startsWith('rue', pos + 1)) break;
pos += 4;
ch = commentWhitespace();
if (ch !== 44/*,*/) break;
pos++;
ch = commentWhitespace();
if (ch !== 103/*g*/ || source.slice(pos + 1, pos + 3) !== 'et') break;
if (ch !== 103/*g*/ || !source.startsWith('et', pos + 1)) break;
pos += 3;
ch = commentWhitespace();
if (ch !== 58/*:*/) break;
pos++;
ch = commentWhitespace();
if (ch !== 102/*f*/ || source.slice(pos + 1, pos + 8) !== 'unction') break;
if (ch !== 102/*f*/ || !source.startsWith('unction', pos + 1)) break;
pos += 8;
ch = commentWhitespace();
if (ch !== 40/*(*/) break;
Expand All @@ -479,16 +479,16 @@ function tryParseObjectDefineOrKeys (keys) {
if (ch !== 123/*{*/) break;
pos++;
ch = commentWhitespace();
if (ch !== 114/*r*/ || source.slice(pos + 1, pos + 6) !== 'eturn') break;
if (ch !== 114/*r*/ || !source.startsWith('eturn', pos + 1)) break;
pos += 6;
ch = commentWhitespace();
if (source.slice(pos, pos + id.length) !== id) break;
if (!source.startsWith(id, pos)) break;
pos += id.length;
ch = commentWhitespace();
if (ch !== 91/*[*/) break;
pos++;
ch = commentWhitespace();
if (source.slice(pos, pos + it_id.length) !== it_id) break;
if (!source.startsWith(it_id, pos)) break;
pos += it_id.length;
ch = commentWhitespace();
if (ch !== 93/*]*/) break;
Expand Down Expand Up @@ -534,7 +534,7 @@ function tryParseObjectDefineOrKeys (keys) {

function readExportsOrModuleDotExports (ch) {
const revertPos = pos;
if (ch === 109/*m*/ && source.slice(pos + 1, pos + 6) === 'odule') {
if (ch === 109/*m*/ && source.startsWith('odule', pos + 1)) {
pos += 6;
ch = commentWhitespace();
if (ch !== 46/*.*/) {
Expand All @@ -544,7 +544,7 @@ function readExportsOrModuleDotExports (ch) {
pos++;
ch = commentWhitespace();
}
if (ch === 101/*e*/ && source.slice(pos + 1, pos + 7) === 'xports') {
if (ch === 101/*e*/ && source.startsWith('xports', pos + 1)) {
pos += 7;
return true;
}
Expand All @@ -561,7 +561,7 @@ function tryParseModuleExportsDotAssign () {
if (ch === 46/*.*/) {
pos++;
ch = commentWhitespace();
if (ch === 101/*e*/ && source.slice(pos + 1, pos + 7) === 'xports') {
if (ch === 101/*e*/ && source.startsWith('xports', pos + 1)) {
tryParseExportsDotAssign(true);
return;
}
Expand Down Expand Up @@ -632,7 +632,7 @@ function tryParseExportsDotAssign (assign) {

function tryParseRequire (directStarExport) {
// require('...')
if (source.slice(pos + 1, pos + 7) === 'equire') {
if (source.startsWith('equire', pos + 1)) {
pos += 7;
const revertPos = pos - 1;
let ch = commentWhitespace();
Expand Down Expand Up @@ -1029,7 +1029,7 @@ function keywordStart (pos) {
function readPrecedingKeyword (pos, match) {
if (pos < match.length - 1)
return false;
return source.slice(pos - match.length + 1, pos + 1) === match && (pos === 0 || isBrOrWsOrPunctuatorNotDot(source.charCodeAt(pos - match.length)));
return source.startsWith(match, pos - match.length + 1) && (pos === 0 || isBrOrWsOrPunctuatorNotDot(source.charCodeAt(pos - match.length)));
}

function readPrecedingKeyword1 (pos, ch) {
Expand Down Expand Up @@ -1111,8 +1111,8 @@ function isExpressionKeyword (pos) {
}

function isParenKeyword (curPos) {
return source.charCodeAt(curPos) === 101/*e*/ && source.slice(curPos - 4, curPos) === 'whil' ||
source.charCodeAt(curPos) === 114/*r*/ && source.slice(curPos - 2, curPos) === 'fo' ||
return source.charCodeAt(curPos) === 101/*e*/ && source.startsWith('whil', curPos - 4) ||
source.charCodeAt(curPos) === 114/*r*/ && source.startsWith('fo', curPos - 2) ||
source.charCodeAt(curPos - 1) === 105/*i*/ && source.charCodeAt(curPos) === 102/*f*/;
}

Expand Down Expand Up @@ -1142,11 +1142,11 @@ function isExpressionTerminator (curPos) {
case 41/*)*/:
return true;
case 104/*h*/:
return source.slice(curPos - 4, curPos) === 'catc';
return source.startsWith('catc', curPos - 4);
case 121/*y*/:
return source.slice(curPos - 6, curPos) === 'finall';
return source.startsWith('finall', curPos - 6);
case 101/*e*/:
return source.slice(curPos - 3, curPos) === 'els';
return source.startsWith('els', curPos - 3);
}
return false;
}