Values

• 1: A bit more about numbers

// String values.
// Strings can be concatenated.
console.log("deno" + ".land");

// Number values.
// Numbers support all the usual operations.
// There are no separate types for integer and
// floating point numbers.
console.log("1 + 1 =", 1 + 1);
console.log("2 - 1 =", 2 - 1);
console.log("2 * 2 =", 2 * 2);
console.log("6 / 3 =", 6 / 3);

// Boolean values.
console.log("true =", true);
console.log("false =", false);
console.log("true && false =", true && false);
console.log("true || false =", true || false);
console.log("!true =", !true);
  

deno.land
1 + 1 = 2
2 - 1 = 1
2 * 2 = 4
6 / 3 = 2
true = true
false = false
true && false = false
true || false = true
!true = false
  

1 - A bit more about numbers

TypeScript does not have separate types for integer and float values, only number. Be aware that the computations that result in a floating point value might not be what you’re expecting.

• numbers.ts
• Output

console.log("7 / 3 =", 7 / 3);
console.log("7.0 / 3.0 =", 7.0 / 3.0);
console.log("2.33 * 3 =", 2.33 * 3);
console.log("2.3333333333333335 * 3 =", 2.3333333333333335 * 3);
  

7 / 3 = 2.3333333333333335
7.0 / 3.0 = 2.3333333333333335
2.33 * 3 = 6.99
2.3333333333333335 * 3 = 7
  

You can use Math.ceil, Math.floor, and Math.round to convert to an integer rounded up, down, or to the nearest, respectively.

Try using Deno’s REPL (read-eval-print-loop) for experimenting. Enter deno repl (or just simply deno) in your terminal.

$ deno
Deno 1.12.1
exit using ctrl+d or close()
> Math.ceil(.95)
1
> Math.ceil(7/3)
3
> Math.floor(7/3)
2
> Math.round(7/3)
2

If you want to obtain a string value of the result of a calculation to a particular precision, you can use toPrecision() to specify the number of significant digits.

> (7/3).toPrecision(3)
"2.33"
> (2).toPrecision(4)
"2.000"