rewrite in javascript

node_modules/firstline/test/mocha.opts

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+--reporter spec
+--ui bdd

node_modules/firstline/test/test.js

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+'use strict';
+
+const promisify = require('js-promisify');
+const chai = require('chai');
+const chaiAsPromised = require('chai-as-promised');
+const fs = require('fs');
+const path = require('path');
+const rimraf = require('rimraf');
+
+const firstline = require('../index.js');
+const mocks = require('./mocks.js');
+
+chai.should();
+chai.use(chaiAsPromised);
+
+describe('firstline', () => {
+
+  const dirPath = path.join(__dirname, 'tmp/');
+  const filePath = dirPath + 'test.txt';
+  const wrongFilePath = dirPath + 'no-test.txt';
+
+  before(() => fs.mkdirSync(dirPath)); // Make "tmp" folder
+
+  after(() => rimraf.sync(dirPath)); // Delete "tmp" folder
+
+  describe('#check', () => {
+
+    afterEach(() => rimraf.sync(filePath)); // Delete mock CSV file
+
+    it(
+      'should reject if the file does not exist',
+      () => firstline(wrongFilePath).should.be.rejected
+    );
+
+    it(
+      'should return the first line of a file and default to `\\n` line ending',
+      () => promisify(fs.writeFile, [filePath, 'abc\ndef\nghi'])
+        .then(() => firstline(filePath).should.eventually.equal('abc'))
+    );
+
+    it(
+      'should work correctly if the first line is long',
+      () => promisify(fs.writeFile, [filePath, mocks.longLine])
+        .then(() => firstline(filePath).should.eventually.equal(mocks.longLine.split('\n')[0]))
+    );
+
+    it(
+      'should return an empty line if the file is empty',
+      () => promisify(fs.writeFile, [filePath, ''])
+        .then(() => firstline(filePath).should.eventually.equal(''))
+    );
+
+    it(
+      'should work with a different encoding when specified correctly',
+      () => promisify(fs.writeFile, [filePath, 'abc\ndef\nghi', { encoding: 'ascii' }])
+        .then(() => firstline(filePath, { encoding: 'ascii' }).should.eventually.equal('abc'))
+    );
+
+    it(
+      'should work with a different line ending when specified correctly',
+      () => promisify(fs.writeFile, [filePath, 'abc\rdef\rghi'])
+        .then(() => firstline(filePath, { lineEnding: '\r' }).should.eventually.equal('abc'))
+    );
+
+    it(
+      'should return the entire file if the specified line ending is wrong',
+      () => promisify(fs.writeFile, [filePath, 'abc\ndef\nghi'])
+        .then(() => firstline(filePath, { lineEnding: '\r' }).should.eventually.equal('abc\ndef\nghi'))
+    );
+
+    it(
+      'should handle BOM',
+      () => promisify(fs.writeFile, [filePath, '\uFEFFabc\ndef'])
+        .then(() => firstline(filePath).should.eventually.equal('abc'))
+    );
+
+  });
+
+});