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Since deno is supporting Typescript which is super-set of the JavaScript. It support all the syntax from the JavaScript. However, Deno is a more then that. It also support APIs for file reading and network and etc.

Here below are some examples, that explains how numbers behave in Deno[Javascript].


There are some Gotcha in Number as it is in JavaScript.


function main() {
const num = 10;
const num2: number = 20; // same as above but declarative

let num3: number;
num3 = num + num2;

// num3 = num + "20" // Error, Type 'string' is not assignable to type 'number'
num3 = num + Number("20"); // No error, cast string to number

num3 = num + parseInt("20", 10); // same as above


let flt = 10.0;

console.log(flt === 10); // true

console.log(flt === 10.1); // false

console.log(typeof flt, typeof 10); //number number

console.log(typeof NaN, typeof Infinity, typeof -Infinity); // number number number

console.log(NaN === NaN); // false

console.log(1.2 + 1.8); // 3 NOT 3.0

console.log(1.2 + 1.8 === 3); // true

Things to be noted as in JS, deno also has same number for int and float number. NaN, Infinity are some special NaN.


How to run example:

deno run examples/03_numbers.ts