WEBVTT

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When you create the program or application in JavaScript or in other program language, you might be

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excited by how they work and give us the results.

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But you need to know that our code is not a wizard before we create the programs.

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There has been already created also a program by other smart people which can read our codes, translate

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them and execute in order to make our codes understandable.

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For that program, we need to follow the set of rules, which is called Syntex.

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In Computer Science, the syntax of a computer language is the set of rules that defines the combinations

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of symbols that are considered to be a correctly structured document in that language.

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So the JavaScript syntax is the set of rules, how JavaScript programs are constructed.

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We always need to be assured that the grammar of our code is valid.

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That's the main work of syntax parser, which is the part of JavaScript engine.

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It checks the code character by character and if something is wrong, then it throws an error regarding

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syntax parser and JavaScript engine, we will discuss how they work in depth in comic sections.

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Let's take a look on that example here we have the variable with name, first name and its value, John.

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Maybe you don't know yet what variable is or you may not know from other programming languages, it

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doesn't matter for now because I'm just trying to demonstrate how important it is to write syntactically

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correct code.

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So, as we said, the syntax pasturage the code character by character, when it finds the VR and space,

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it understands that this is a variable declaration, that it expects the name of the variable and finds

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it, which is first name in this case, that it meets the equals sign and finds out that the variable

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has the value, which is, John, after the value, the syntax parser says the semicolon and understands

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that this is the end of the statement.

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So the code is valid and the syntax parser continues to read the next coming Cote's.

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If it meets something like this, it will find that there is no equal sign between name of the variable

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and the value.

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Smith So syntax parser is expecting here the equals sign, but instead of it, it finds other character

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which makes the code invalid and therefore syntax parser throws an error.

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All right, let's write the same example in brackets.

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Their first name equals the John.

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Then last name.

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Smith.

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Reload the page and you see we have syntax error on the third line in script, I just file, it tells

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us that we have unexpected string value.

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If we place your equal sign that the code will work all right throughout the course, you will learn

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how to write the appellate code that will help you to avoid getting errors and mistakes.

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But anyway, errors and bugs are our friends because they are the best teachers to write the code correctly.

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OK, in this lecture, we have talked about the syntax and how the syntax parser with the code line

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by line and character by character.

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See you in the next video.