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prev: The implementation of JavaScript's `number s is based on the `IEEE 754` standard, often called "floating-point." my changes: The implementation of JavaScript's `numbers is based on the `IEEE 754` standard, often called "floating-point."
91 lines
2.7 KiB
Markdown
91 lines
2.7 KiB
Markdown
---
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title: Numbers
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---
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## Numbers
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The implementation of JavaScript's `numbers is based on the `IEEE 754` standard, often called "floating-point."
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<a href='https://en.wikipedia.org/wiki/IEEE_754' target='_blank' rel='nofollow'>IEEE 754 Wikipedia Link</a>
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<br>
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<a href='http://bartaz.github.io/ieee754-visualization/' target='_blank' rel='nofollow'>IEEE 754 Double Precision Floating Point Visualization</a>
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Number literals are expressed generally as `base-10` decimal literals.
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```javascript
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var foo = 47;
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var bar = 47.9;
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```
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The leading portion of a decimal value, if `0`, is optional:
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```javascript
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var same = 0.47;
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var stillSame = .47;
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```
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Similarly, the trailing portion (the fractional) of a decimal value after the `.`, if `0`, is optional:
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```javascript
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var a = 47.0;
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var b = 47.;
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```
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By default, most numbers will be outputted as `base-10` decimals, with trailing fractional `0`s removed. So:
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```javascript
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var foo = 47.300;
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var bar = 47.0;
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foo; // 47.3
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bar; // 47
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```
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Very large or very small `numbers` can be written as:
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```javascript
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var foo = 47e8; // 4700000000
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var baz = 47e-8; // 00.00000047
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```
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`toExponential` method can be used to convert a `number` into its `exponential notation`.
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```javascript
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var foo = 47e8;
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foo; // 4700000000
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foo.toExponential() //"47e8"
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```
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Numbers have access to methods that are built into `Number.prototype`.
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For Example:
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`toFixed()` method formats a number with a specific number of digits to the right of the decimal.
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```javascript
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var foo = 47.69;
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foo.toFixed(0); // "48"
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foo.toFixed(1); // "47.7"
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foo.toFixed(2); // "47.69"
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```
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>Type `Number.prototype` in your browser and see other available methods yourself.
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Numbers in strings are treated differently than normal numbers.
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```javascript
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var foo = "12" + 18; // "1218"
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```
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In order to convert a string into a number you must run it through a ```Number()``` function.
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```javascript
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var foo = "12";
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var bar = Number(foo) + 18; // "30"
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```
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#### More Information:
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1. <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type' target='_blank' rel='nofollow'>MDN</a>
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2. <a href='https://www.w3schools.com/js/js_numbers.asp' target='_blank' rel='nofollow'>JavaScript Numbers</a>
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#### References
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1. <a href='https://github.com/getify/You-Dont-Know-JS/tree/master/types%20%26%20grammar' target='_blank' rel='nofollow'>Types & grammar</a> by Kyle Simpson.
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2. <a href='https://www.ecma-international.org/ecma-262/5.1/#sec-4.3.20' target='_blank' rel='nofollow'>ECMAScript Language Specification: 4.3.20</a>
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3. <a href='https://www.ecma-international.org/ecma-262/5.1/#sec-15.7' target='_blank' rel='nofollow'>ECMAScript Language Specification: 15.7 Number Objects</a>
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