Use const and let instead of var.

Closes #227

Author: RubenVerborgh

.eslintrc

@@ -107,7 +107,7 @@
     no-undef: 2,
     no-undefined: 0,
     no-unused-vars: [ 2, { args: "none" }],
-    no-use-before-define: [2, "nofunc"],
+    no-use-before-define: [2, { functions: false }],
 
     // Node.js
     callback-return: 0,
@@ -143,6 +143,7 @@
     new-parens: 2,
     newline-after-var: 0,
     no-array-constructor: 2,
+    no-const-assign: 2,
     no-continue: 2,
     no-inline-comments: 0,
     no-lonely-if: 2,
@@ -155,6 +156,7 @@
     no-trailing-spaces: 2,
     no-underscore-dangle: 0,
     no-unneeded-ternary: 2,
+    no-var: 2,
     object-curly-spacing: [2, "always"],
     object-curly-newline: 0,
     object-property-newline: 0,
@@ -163,6 +165,7 @@
     operator-linebreak: [2, "after", { overrides: { ":": "ignore" } }],
     padded-blocks: [2, "never"],
     prefer-arrow-callback: 2,
+    prefer-const: 2,
     quote-props: [2, "consistent-as-needed"],
     quotes: [2, "single", "avoid-escape"],
     semi-spacing: 2,

perf/N3Lexer-perf.js

@@ -1,19 +1,19 @@
 #!/usr/bin/env node
-var N3 = require('..');
-var fs = require('fs'),
+const N3 = require('..');
+const fs = require('fs'),
     assert = require('assert');
 
 if (process.argv.length !== 3) {
   console.error('Usage: N3Lexer-perf.js filename');
   process.exit(1);
 }
 
-var filename = process.argv[2];
+const filename = process.argv[2];
 
-var TEST = '- Lexing file ' + filename;
+const TEST = '- Lexing file ' + filename;
 console.time(TEST);
 
-var count = 0;
+let count = 0;
 new N3.Lexer().tokenize(fs.createReadStream(filename), (error, token) => {
   assert(!error, error);
   count++;

perf/N3Parser-perf.js

@@ -1,6 +1,6 @@
 #!/usr/bin/env node
-var N3 = require('..');
-var fs = require('fs'),
+const N3 = require('..');
+const fs = require('fs'),
     path = require('path'),
     assert = require('assert');
 
@@ -9,13 +9,13 @@ if (process.argv.length !== 3) {
   process.exit(1);
 }
 
-var filename = path.resolve(process.cwd(), process.argv[2]),
+const filename = path.resolve(process.cwd(), process.argv[2]),
     base = 'file://' + filename;
 
-var TEST = '- Parsing file ' + filename;
+const TEST = '- Parsing file ' + filename;
 console.time(TEST);
 
-var count = 0;
+let count = 0;
 new N3.Parser({ baseIRI: base }).parse(fs.createReadStream(filename), (error, quad) => {
   assert(!error, error);
   if (quad)

perf/N3Store-perf.js

@@ -1,21 +1,20 @@
 #!/usr/bin/env node
-var N3 = require('..');
-var assert = require('assert');
+const N3 = require('..');
+const assert = require('assert');
 
 console.log('N3Store performance test');
 
-var prefix = 'http://example.org/#';
-var TEST, dim, dimSquared, dimCubed, dimQuads, store;
+const prefix = 'http://example.org/#';
 
 /* Test triples */
-dim = Number.parseInt(process.argv[2], 10) || 256;
-dimSquared = dim * dim;
-dimCubed = dimSquared * dim;
+let dim = Number.parseInt(process.argv[2], 10) || 256;
+let dimSquared = dim * dim;
+let dimCubed = dimSquared * dim;
 
-store = new N3.Store();
-TEST = '- Adding ' + dimCubed + ' triples to the default graph';
+let store = new N3.Store();
+let TEST = '- Adding ' + dimCubed + ' triples to the default graph';
 console.time(TEST);
-var i, j, k, l;
+let i, j, k, l;
 for (i = 0; i < dim; i++)
   for (j = 0; j < dim; j++)
     for (k = 0; k < dim; k++)
@@ -58,10 +57,10 @@ console.timeEnd(TEST);
 console.log();
 
 /* Test quads */
-dim /= 4,
+dim /= 4;
 dimSquared = dim * dim;
 dimCubed = dimSquared * dim;
-dimQuads = dimCubed * dim;
+const dimQuads = dimCubed * dim;
 
 store = new N3.Store();
 TEST = '- Adding ' + dimQuads + ' quads';

spec/parser.js

@@ -1,4 +1,4 @@
-var StreamParser = require('..').StreamParser;
+const { StreamParser } = require('..');
 
 // Implements the IParser interface from rdf-test-suite
 // https://github.com/rubensworks/rdf-test-suite.js/blob/master/lib/testcase/rdfsyntax/IParser.ts

src/IRIs.js

@@ -1,4 +1,4 @@
-var RDF  = 'http://www.w3.org/1999/02/22-rdf-syntax-ns#',
+const RDF  = 'http://www.w3.org/1999/02/22-rdf-syntax-ns#',
     XSD  = 'http://www.w3.org/2001/XMLSchema#',
     SWAP = 'http://www.w3.org/2000/10/swap/';
 

src/N3DataFactory.js

@@ -5,6 +5,7 @@ import namespaces from './IRIs';
 import { isDefaultGraph } from './N3Util';
 const { rdf, xsd } = namespaces;
 
+// eslint-disable-next-line prefer-const
 let DEFAULTGRAPH;
 let _blankNodeCounter = 0;
 
@@ -78,7 +79,8 @@ export class Literal extends Term {
   // ### The language of this literal
   get language() {
     // Find the last quotation mark (e.g., '"abc"@en-us')
-    var id = this.id, atPos = id.lastIndexOf('"') + 1;
+    const id = this.id;
+    let atPos = id.lastIndexOf('"') + 1;
     // If "@" it follows, return the remaining substring; empty otherwise
     return atPos < id.length && id[atPos++] === '@' ? id.substr(atPos).toLowerCase() : '';
   }
@@ -91,11 +93,12 @@ export class Literal extends Term {
   // ### The datatype string of this literal
   get datatypeString() {
     // Find the last quotation mark (e.g., '"abc"^^http://ex.org/types#t')
-    var id = this.id, dtPos = id.lastIndexOf('"') + 1, ch;
+    const id = this.id, dtPos = id.lastIndexOf('"') + 1;
+    const char = dtPos < id.length ? id[dtPos] : '';
     // If "^" it follows, return the remaining substring
-    return dtPos < id.length && (ch = id[dtPos]) === '^' ? id.substr(dtPos + 2) :
+    return char === '^' ? id.substr(dtPos + 2) :
            // If "@" follows, return rdf:langString; xsd:string otherwise
-           (ch !== '@' ? xsd.string : rdf.langString);
+           (char !== '@' ? xsd.string : rdf.langString);
   }
 
   // ### Returns whether this object represents the same term as the other
@@ -202,7 +205,7 @@ export function termFromId(id, factory) {
     if (id[id.length - 1] === '"')
       return factory.literal(id.substr(1, id.length - 2));
     // Literal with datatype or language
-    var endPos = id.lastIndexOf('"', id.length - 1);
+    const endPos = id.lastIndexOf('"', id.length - 1);
     return factory.literal(id.substr(1, endPos - 1),
             id[endPos + 1] === '@' ? id.substr(endPos + 2)
                                    : factory.namedNode(id.substr(endPos + 3)));

src/N3Lexer.js

@@ -5,17 +5,17 @@ import queueMicrotask from 'queue-microtask';
 const { xsd } = namespaces;
 
 // Regular expression and replacement string to escape N3 strings
-var escapeSequence = /\\u([a-fA-F0-9]{4})|\\U([a-fA-F0-9]{8})|\\([^])/g;
-var escapeReplacements = {
+const escapeSequence = /\\u([a-fA-F0-9]{4})|\\U([a-fA-F0-9]{8})|\\([^])/g;
+const escapeReplacements = {
   '\\': '\\', "'": "'", '"': '"',
   'n': '\n', 'r': '\r', 't': '\t', 'f': '\f', 'b': '\b',
   '_': '_', '~': '~', '.': '.', '-': '-', '!': '!', '$': '$', '&': '&',
   '(': '(', ')': ')', '*': '*', '+': '+', ',': ',', ';': ';', '=': '=',
   '/': '/', '?': '?', '#': '#', '@': '@', '%': '%',
 };
-var illegalIriChars = /[\x00-\x20<>\\"\{\}\|\^\`]/;
+const illegalIriChars = /[\x00-\x20<>\\"\{\}\|\^\`]/;
 
-var lineModeRegExps = {
+const lineModeRegExps = {
   _iri: true,
   _unescapedIri: true,
   _simpleQuotedString: true,
@@ -26,7 +26,7 @@ var lineModeRegExps = {
   _whitespace: true,
   _endOfFile: true,
 };
-var invalidRegExp = /$0^/;
+const invalidRegExp = /$0^/;
 
 // ## Constructor
 export default class N3Lexer {
@@ -57,7 +57,7 @@ export default class N3Lexer {
     if (this._lineMode = !!options.lineMode) {
       this._n3Mode = false;
       // Don't tokenize special literals
-      for (var key in this) {
+      for (const key in this) {
         if (!(key in lineModeRegExps) && this[key] instanceof RegExp)
           this[key] = invalidRegExp;
       }
@@ -77,10 +77,11 @@ export default class N3Lexer {
   // ### `_tokenizeToEnd` tokenizes as for as possible, emitting tokens through the callback
   _tokenizeToEnd(callback, inputFinished) {
     // Continue parsing as far as possible; the loop will return eventually
-    var input = this._input, outputComments = this._comments;
+    let input = this._input;
+    const outputComments = this._comments;
     while (true) {
       // Count and skip whitespace lines
-      var whiteSpaceMatch, comment;
+      let whiteSpaceMatch, comment;
       while (whiteSpaceMatch = this._newline.exec(input)) {
         // Try to find a comment
         if (outputComments && (comment = this._comment.exec(whiteSpaceMatch[0])))
@@ -106,8 +107,9 @@ export default class N3Lexer {
       }
 
       // Look for specific token types based on the first character
-      var line = this._line, type = '', value = '', prefix = '',
-          firstChar = input[0], match = null, matchLength = 0, inconclusive = false;
+      const line = this._line, firstChar = input[0];
+      let type = '', value = '', prefix = '',
+          match = null, matchLength = 0, inconclusive = false;
       switch (firstChar) {
       case '^':
         // We need at least 3 tokens lookahead to distinguish ^^<IRI> and ^^pre:fixed
@@ -343,7 +345,7 @@ export default class N3Lexer {
       }
 
       // Emit the parsed token
-      var token = { line: line, type: type, value: value, prefix: prefix };
+      const token = { line: line, type: type, value: value, prefix: prefix };
       callback(null, token);
       this.previousToken = token;
       this._previousMarker = type;
@@ -418,7 +420,7 @@ export default class N3Lexer {
   // ### `_syntaxError` creates a syntax error for the given issue
   _syntaxError(issue) {
     this._input = null;
-    var err = new Error('Unexpected "' + issue + '" on line ' + this._line + '.');
+    const err = new Error('Unexpected "' + issue + '" on line ' + this._line + '.');
     err.context = {
       token: undefined,
       line: this._line,
@@ -442,8 +444,9 @@ export default class N3Lexer {
         queueMicrotask(() => this._tokenizeToEnd(callback, true));
       // If no callback was passed, tokenize synchronously and return
       else {
-        var tokens = [], error;
-        this._tokenizeToEnd((e, t) => { e ? (error = e) : tokens.push(t); }, true);
+        const tokens = [];
+        let error;
+        this._tokenizeToEnd((e, t) => e ? (error = e) : tokens.push(t), true);
         if (error) throw error;
         return tokens;
       }