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JAVA SCRIPT
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As mentioned on the previous page, any group of characters
between quotes is called a string. Either single or double quotes
will do. Just as variables can hold numbers, variables can hold
strings. So it's legal to say:
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var nice_monkey = "The monkey smiles at you and recites Shakespeare.";
var bad_monkey = "The monkey scowls at you and burps.";
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Sticking these statements into a JavaScript declares the
variables nice_monkey and bad_monkey and makes
them equivalent to these strings. Once you've done this, you can
write
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document.writeln(nice_monkey);
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whenever you want JavaScript to write out the long message
about what nice monkeys do.
Here's an example of what you can do with strings.
View Source and we'll go through the new and interesting parts
of this script.
The script starts with something new:
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var monkey = prompt("What's the monkey's name?", "The monkey");
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we're calling the prompt method to get input from a user. When the
prompt method is called, it brings up a dialog box that asks for a
user's input. When the user hits OK, the prompt returns whatever
is in the input box. In the above line, this returned value gets
put into the monkey variable.
Notice that the prompt method takes two parameters, both of
which are strings. The first parameter is what gets printed above
the input field in the dialog box. In this case it's, "What's
the monkey's name?" The second parameter, "The
monkey" in this example, is set as the default value of the
input box. If you don't want a default value, just put two quote
marks as the second parameter. Like this:
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var monkey = prompt("What's the monkey's name?", "");
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The next lines are a few straightforward variable assignments,
like we've seen before. After these lines we see:
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var techy_monkey = monkey + demanding + tech;
This line introduces a string operator: the plus sign. When the
plus sign appears between two strings, or two variables that
contain strings as above, it means " concatenate."
So the above line creates a new variable called techy_monkey
that contains a string made of whatever the three variables
contain. In this case, it's "The monkey" +
"demands, no, insists upon receiving" + "a
computer that won't crash, and a homemade browser!" In
other words, |
var techy_monkey = monkey + demanding + tech;
var techy_monkey = "The monkey demands, no, insists upon receiving a computer
that won't crash, and a homemade browser!";
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The next bunch of lines show some more tricks you can do with
strings. All the tricks work in similar ways, so we'll just look
at three of them:
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var italic_hippy = hippy_monkey.italics();
var shouting_hippy= hippy_monkey.toUpperCase();
var red_bold_tech = bold_tech.fontcolor('red');
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first of these lines says, "Take the string that's contained
in the variable hippy_monkey and put it in italics
tags." It's actually the same thing as saying
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var italic_hippy = "<i>" + hippy_monkey + "</i>";
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it looks much nicer. In either case, when you later write document.writeln(italic_hippy)
in your JavaScript, you get the string in hippy_monkey
printed in italics.
The next line, which declares shouting_hippy, shows a
string trick that you can't do with HTML. It takes whatever's in hippy_monkey
and makes all the letters uppercase.
The third line shows an example of changing a property of a
string. All strings have color, and you can change the color of a
string using the string.fontcolor('new color'); command.
You could also do this:
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var red_bold_tech = "<font color='red'>" + bold_tech + "</font>";
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but that's not as easy to read as
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var red_bold_tech = bold_tech.fontcolor('red');
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You've seen everything else in this example except this line:
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document.writeln(bold_tech + "<br>");
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This is just a normal document.writeln(), except
instead of just printing a string, we're concatenating two strings
and then printing the result. This could have been done in two
lines, like this:
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var broken_bold = bold_tech + "<br>";
document.writeln(broken_bold);
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that would involve creating
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