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| // ------------------------------------------------ | |
| // Update elements of an object (key - value) by index number not name | |
| const obj = { | |
| student1: { | |
| country: 'Chile', | |
| name: 'Tom' | |
| }, | |
| student2: { | |
| country: 'Argentina', | |
| name: 'Julia' | |
| } | |
| }; | |
| console.log(obj); | |
| Object.values(obj)[0].country = 'USA'; | |
| console.log(obj); | |
| // ------------------------------------------------ | |
| // Synchronously read a file line by line without loading all of it into memory | |
| // Inspired from: https://stackoverflow.com/questions/7545147/nodejs-synchronization-read-large-file-line-by-line | |
| import fs from 'fs'; | |
| const filename: string = 'gds_result.txt' | |
| const fd: number = fs.openSync(filename, 'r'); | |
| const bufferSize: number = 1024; | |
| const buffer: Buffer = Buffer.alloc(bufferSize); | |
| let leftOver: string = ''; | |
| let read: number, line: string, idxStart: number, idx: number; | |
| // while buffer is not empty/0 get more 1024 more bytes | |
| while ((read = fs.readSync(fd, buffer, 0, bufferSize, null)) !== 0) { | |
| // line content here | |
| leftOver += buffer.toString('utf8', 0, read); | |
| idxStart = 0 | |
| // Only executes if there is a newline in the buffered content | |
| while ((idx = leftOver.indexOf('\n', idxStart)) !== -1) { | |
| // remove everything before the newline | |
| line = leftOver.substring(idxStart, idx); | |
| idxStart = idx + 1; | |
| console.log('One line read: ' + line); | |
| } | |
| // keep the rest of the buffer for the next iteration | |
| leftOver = leftOver.substring(idxStart); | |
| } | |
| // Asynchronous method for reading a file line by line | |
| import fs from 'fs'; | |
| import readline, { Interface } from 'readline'; | |
| let line_counter: number = 0; | |
| const rl: Interface = readline.createInterface({ | |
| input: fs.createReadStream("./gds_result.txt"), | |
| crlfDelay: Infinity | |
| }); | |
| rl.on('line', (line: string) => { | |
| line_counter++; | |
| console.log(`${line_counter}: ${line}`); | |
| }); | |
| // how to add a method to Number base class | |
| // allows extension of Number type | |
| // must use declare global if in index file; normally people create a separate module: | |
| // Number.extensions.ts and import that | |
| declare global { | |
| interface Number { | |
| sum(a: number): number; | |
| } | |
| } | |
| Number.prototype.sum = function (a: number) { | |
| return Number(this) + a; | |
| }; | |
| console.log(typeof (2).sum(3)); | |
| // extend base class formally with typescript | |
| // https://stackoverflow.com/questions/27050584/is-it-possible-to-have-a-class-extend-number | |
| /** | |
| * Decimal class | |
| * Represents a decimal number with a fixed precision which can be defined in the constructor. | |
| * | |
| * @export | |
| * @class Decimal | |
| * @extends { Number } | |
| * @implements { Number } | |
| */ | |
| export class Decimal extends Number implements Number { | |
| public precision: number; | |
| /** | |
| * Creates an instance of Decimal. | |
| * | |
| * @param {(number | string)} value | |
| * | |
| * @memberOf Decimal | |
| */ | |
| constructor(value: number | string, precision: number = 2) { | |
| if (typeof value === 'string') { | |
| value = parseFloat(value); | |
| } | |
| if (typeof value !== 'number' || isNaN(value)) { | |
| throw new Error('Decimal constructor requires a number or the string representation of a number.'); | |
| } | |
| super(parseFloat((value || 0).toFixed(2))); | |
| this.precision = precision; | |
| } | |
| } | |
| const yeet = new Decimal(1.23456789, 4); | |
| // buffers and arraybuffers; useful for laying out a raw binary communication protocol | |
| const dataBuf = new ArrayBuffer(10) // basically a raw array | |
| const dv = new DataView(dataBuf); // a way to get data from the array in tranches | |
| console.log(dataBuf); | |
| // set the values | |
| dv.setUint8(0, 2); //msgType | |
| dv.setFloat32(1, 252.55); //x | |
| dv.setFloat32(5, 848.32); //y | |
| dv.setUint8(9, 4); //player id | |
| // console.log(dataBuf); | |
| const msgType = dv.getUint8(0); | |
| const x = dv.getFloat32(1); | |
| const y = dv.getFloat32(5); | |
| const playerID = dv.getUint8(9); | |
| console.log(`Msg Type: ${msgType}\nx: ${x}\ny: ${y}\nPlayer ID: ${playerID}`); | |
| [ | |
| 2, // msgType (uint8 = 1 byte) | |
| _, _, _, _, // x (float32 = 4 bytes) | |
| _, _, _, _, // y (float32 = 4 bytes) | |
| 4 // playerID (uint8 = 1 byte) | |
| ] |
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