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JS determines whether an array contains a certain value

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2020-05-30 18:01:4610712browse

JS determines whether an array contains a certain value

#How does js determine a value in an array?

The function in js to determine whether an array contains a certain value is "indexOf". The specific usage is as follows:

The indexOf() method returns the first occurrence of a specified string value in a string.

Syntax

stringObject.indexOf(searchvalue,fromindex)
Parameters Description
searchvalue
Required. Specifies the string value to be retrieved.
fromindex
Optional integer parameter. Specifies the position in the string to begin searching. Its legal values ​​are 0 to stringObject.length - 1. If this parameter is omitted, the search will start from the first character of the string.

Note: The indexOf() method is case-sensitive!

Note: If the string value to be retrieved does not appear, this method returns -1.

Specific usage:

First create an html file, add the following code:

<html>
<body>
<script type="text/javascript">
var str="Hello world!"
document.write(str.indexOf("Hello") + "<br />")
</script>
</body>
</html>

Then run the html file in the browser

Finally, check the running results. "-1" means that this value does not exist;

Related references: JS Tutorial

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