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When programming in any language.

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It's very common to create logic that performs different actions based on one or more conditions.

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JavaScript has a variety of conditional statements that will explore in this lesson we'll be exploring

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the if else and else if statements these statements allow us to execute an action contained within a

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block of code.

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If certain conditions are met let's take a look at how this works with a simple example will create

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a script that converts a student's numerical test score into a letter grade to keep it simple we'll

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assume the test was out of 100 marks.

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First we need to define the grading system let's say that a score of zero to forty nine equals an F

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fifty two sixty nine equals a d seventy to seventy nine equals a C eighteen to eighty nine equals A

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B and 90 to 100 one hundred inclusive equals and a

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in order to do this.

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We need to start by creating our test score variable and assigning a value

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called the variable score and we'll assign a value of sixty five for now keep in mind that we'll make

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changes to this score to test our script later on.

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Next we'll need to start with our first if statement if the score is less than 50.

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We want to output an F so start by typing.

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If

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score is less than 50

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you will output an F using the document write method.

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If the score is greater than 50 but less than 70 we want to output a D.

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Since we're adding a condition to our original if statement we must start this condition with the.

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Else if statement

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a copy this.

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Else if statement because when you create a few others so the next one we need is if the score is greater

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than 70 but less than 80.

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We want to output a C

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this is for if the score is greater than 80 but less than 90 will output a B

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and if the score is greater than 90 or equal to 100 we want to output on a

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the last thing we want to do is if this score is anything above one hundred we need to display an error

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message indicating that the score must be less than 100 because the exam was out of one hundred marks

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for this we'll use the L statement the L statement instructs the script on what to do.

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If none of the preceding conditions have been met

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in I'll go ahead and save this file and previewed in our web browser.

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So here we have

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d that has been output.

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Because our current score we've set it to sixty five.

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Now that is greater than 50 in less than 70.

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So if we were to change our score let's go ahead and change the score to 81

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and in this case it correctly outputs a B because that's over 80 but less and less than 90.

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Now let's see what will happen if we create a score above 100

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is where our L statement is working.

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The score must be less than 100 and so you can go ahead and play with that.

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But that's basically how the if else if and l statements were also known as conditional statements.