Get String Length with Javascript

I am writing JavaScripts and i need to know what strings are and how they work. I have tried to create a code to find the length of a string with str.length() function but gives error. Can any one tell me how to find the length of a string in JavaScripts.

Code:

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<script type="text/javascript">
var myString = "12345678";

var length = mstr.length;

document.write("The string length : " + length);

document.write("<br />The string is this long: " + myString.length);

</script>

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Output :

Code:

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The string is this long: 8
The string is this long: 8

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Javascript string length :

The following example uses the length property of the String object to find the length of a string:var txt="string";
document.write(text1.length);

The code above will result in the following output:6

The following example uses the toUpperCase() method of the String object to convert a string to uppercase letters:var txt="string";document.write(txt.toUpperCase());

The code above will result in the following output:string

Strings are simply groups of characters, like 'JavaScript', 'string',

Code:

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<script language="javascript" type="text/javascript">

var len=" length of chracter";
alert(len.length);

</script>

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