Merge branch 'master' of https://github.com/iliakan/javascript-tutorial-en
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# An introduction to JavaScript
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# An Introduction to JavaScript
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Let's see what's so special about JavaScript, what we can achieve with it and which other technologies play well with it.
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@ -201,7 +201,7 @@ Funny code, isn't it? We should understand how it works, because sometimes we ca
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## Remainder %
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The remainder operator `%` despite it's look does not have a relation to percents.
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The remainder operator `%` despite its look does not have a relation to percents.
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The result of `a % b` is the remainder of the integer division of `a` by `b`.
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@ -415,7 +415,7 @@ let a = (1+2, 3+4);
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alert( a ); // 7 (the result of 3+4)
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```
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Here, the first expression `1+2` is evaluated, and it's result is thrown away, then `3+4` is evaluated and returned as the result.
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Here, the first expression `1+2` is evaluated, and its result is thrown away, then `3+4` is evaluated and returned as the result.
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```smart header="Comma has a very low precedence"
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Please note that the comma operator has very low precedence, lower than `=`, so parentheses are important in the example above.
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@ -155,6 +155,7 @@ switch (arg) {
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case '0':
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case '1':
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alert( 'One or zero' );
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break;
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case '2':
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alert( 'Two' );
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case 3:
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alert( 'Never executes!' );
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break;
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default:
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alert( 'An unknown value' )
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}
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@ -316,7 +316,7 @@ The result of a property access `user.hi` is not a function, but a value of Refe
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When parentheses `()` are called on the Reference Type, they receive the full information about the object and it's method, and can set the right `this` (`=user` in this case).
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Any other operation like assignment `hi = user.hi` discards the reference type as a whole, takes the value of `user.hi` (a function) and passes it on. So any further operation "looses" `this`.
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Any other operation like assignment `hi = user.hi` discards the reference type as a whole, takes the value of `user.hi` (a function) and passes it on. So any further operation "loses" `this`.
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So, as the result, the value of `this` is only passed the right way if the function is called directly using a dot `obj.method()` or square brackets `obj[method]()` syntax (they do the same here).
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@ -1,7 +1,7 @@
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# Object to primitive conversion
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What happens when objects are added `obj1 + obj2`, substracted `obj1 - obj2` or printed using `alert(obj)`?
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What happens when objects are added `obj1 + obj2`, subtracted `obj1 - obj2` or printed using `alert(obj)`?
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There are special methods in objects that do the conversion.
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For objects, there's no to-boolean conversion, because all objects are `true` in a boolean context. So there are only string and numeric conversions.
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The numeric conversion happens when we substract objects or apply mathematical functions. For instance, `Date` objects (to be covered in the chapter <info:date>) can be substracted, and the result of `date1 - date2` is the time difference between two dates.
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The numeric conversion happens when we subtract objects or apply mathematical functions. For instance, `Date` objects (to be covered in the chapter <info:date>) can be subtracted, and the result of `date1 - date2` is the time difference between two dates.
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As for the string conversion -- it usually happens when we output an object like `alert(obj)` and in similar contexts.
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@ -162,16 +162,16 @@ alert( new SmallUser().name ); // John
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Usually constructors don't have a `return` statement. Here we mention the special behavior with returning objects mainly for the sake of completeness.
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````smart header="Omitting brackets"
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By the way, we can omit brackets after `new`, if it has no arguments:
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````smart header="Omitting parentheses"
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By the way, we can omit parentheses after `new`, if it has no arguments:
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```js
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let user = new User; // <-- no brackets
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let user = new User; // <-- no parentheses
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// same as
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let user = new User();
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```
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Omitting brackets here is not considered a "good style", but the syntax is permitted by specification.
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Omitting parentheses here is not considered a "good style", but the syntax is permitted by specification.
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````
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## Methods in constructor
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@ -4,7 +4,7 @@ Objects allow to store keyed collections of values. That's fine.
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But quite often we find that we need an *ordered collection*, where we have a 1st, a 2nd, a 3rd element and so on. For example, we need that to store a list of something: users, goods, HTML elements etc.
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It not convenient to use an object here, because it provides no methods to manage the order of elements. We can’t insert a new property “between” the existing ones. Objects are just not meant for such use.
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It is not convenient to use an object here, because it provides no methods to manage the order of elements. We can’t insert a new property “between” the existing ones. Objects are just not meant for such use.
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There exists a special data structure named `Array`, to store ordered collections.
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