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Applications that require users
to sign up and sign in often

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have unique constraint requirements for
passwords and other form fields.

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Password fields can require verification
that certain characters are included in

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a password string.

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You may need to determine if an email
address ends with a specific

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string like dot edu.

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This small piece of a larger
string is called a substring.

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JavaScript provides strings with multiple
options for searching for substrings.

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The first method we'll explore is indexOf.

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The indexOf method returns
the position of the first occurrence

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of a specified value in a string.

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If the substring is present, the method
returns the index where it occurs.

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If the substring is not present,
the method returns the value -1.

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Let's try this out in the workspace
associated with this video.

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Open up a preview of the index.html

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file associated with this
project by clicking the eye icon.

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For this step, we'll be working with
the code in the search.js file.

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There, we have a string
with the value team.

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In the console of our preview, let's
run the indexOf method on index string.

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We'll pass it a value i to see
where i occurs in the spring.

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We get -1 because there's no i in team.

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Now let's try to find the index of tree
in our school variable that stores

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the value treehouse.

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Because the substring starts at the
beginning of the string, 0 is returned.

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Strings also have a method
called lastIndexOf.

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Can you guess what this method does?

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LastIndexOf searches for

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a substring starting from the strings
end instead of the first character.

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For example,

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school.indexOf("e") returns 2.

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But school.last indexOf("e"),

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Returns 8, because the e at
the eighth index position is

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the first e from the end of the string.

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Let's clear up the console
before we go any further.

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IndexOf tells us where a substring is, but

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sometimes we only want to know
if a substring is present.

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For this,
we can use the handy includes method.

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Includes takes a search string and
an optional index to start searching.

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It returns true if the search
string is present and false if not.

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Let's replace indexOf in one of our
previous examples with includes.

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We'll try school.includes("tree").

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And we get the value true.

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We can use the starts with and
ends with methods to check for

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substrings at either the start or
end of strings.

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We'll clear the console again.

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In our search.js, we have a variable
named childrensStory that stores a value,

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Once upon a time not long ago,
and ends with the end.

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For practice, we'll write a program
that checks if strings meant

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to be fairy tales start with
the substring, Once upon a time.

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We'll take our childrensStory variable,
use the startsWith method.

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And pass it the value once upon a time.

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We get a value of true.

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Now let's check that the story
ends with the proper, the end.

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Again, we'll use our
childrensStory variable.

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EndsWith passing it a value of the end.

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And we get true again.

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In the next video, I'll share a set of
methods you can use when you want to

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modify a string value, and
return a new object with that value.