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Global functions
Global, or top level functions, are functions in JavaScript that are independent of any particular object.
Global functions
Note: "[]" surrounding a parameter below means the parameter is optional.
Operator | Description |
---|---|
encodeURI() new | Used to encode the full URI, not including any
parameters added to it , for special characters. For example, it
should be used to encode: http://javascriptkit.com/illegal space.htm but NOT http://javascriptkit.com/illegal space.htm?name=John&age=18 This is because |
encodeURIComponent() new | Used to encode the parameter portion of a URI
for characters that have special meaning, to separate them from
reserved characters such as "&" that act as key/value separators.
More inclusive than encodeURI() , it encodes all
characters with special meaning in a URL string, including "=" and
"&". Use this method only on the parameter portion of a URI;
otherwise, the URI may no longer be valid if it contains one of the
characters that are part of a valid URI (ie: "+") yet should be
escaped if part of the URI parameter.Example: var
username=document.getElementbyId("username").value |
decodeURI() new | Decodes all special characters within a
string that encodeURI() may have encoded. |
decodeURIComponent() new | Decodes all special characters within a
string that decodeURIComponent() may have encoded. |
parseInt(x, [radix]) | Parses any string "x" and returns the
first valid number (integer) it encounters. If the first character
in the string is not a number, white spaces, or a leading minus
sign, parseInt() returns
NaN
instead. You can test for NaN using the isNaN() function below. parseInt() supports an optional 2nd "radix" parameter to specify the base of the number to be parsed (valid range is 2-36). Entering "10" would parse the number in the familiar decimal system, while "16" would be hexadecimal. Without this parameter present, parseInt() assumes any number that begins with "0x" to be radix 16, "0" to be radix 8, and any other number to be radix 10. Examples: parseInt("3 chances") //returns 3 |
parseFloat(x) | Parses any string "x" and returns the
first valid floating point number it encounters. Use this function
to extract numbers with decimals, for example. If the first
character in the string is not a number, white spaces, or a leading
minus sign, parseFloat() returns
NaN
instead. You can test for NaN using the isNaN() function below. Example: parseFloat("-3.98 points") //returns -3.98 |
isNaN(x) | isNaN() checks its parameter "x" to see if it's the value "NaN" (not a number)- an illegal number. The function returns true if "x" is NaN, and false if not. A common example of NaN is 0 divided by 0. This function is required to detect NaN, as using equality operators (== or ===) won't do. |
isFinite(x) | Determines whether a number is finite. Returns false if x is +infinity, -infinity, or NaN. JavaScript 1.3 statement. |
eval(s) | Evaluates the string ("s") and returns
the results of the evaluation (if available). Eval() allows you to dynamically
construct a JavaScript statement or expression. Examples: eval("8+3+1") //returns 12 |
alert(), confirm() and prompt()
These three methods of the Window object are often confused as top-level functions (since the "window" prefix is typically omitted when using them), so we'll listing them here just for your convenience. You can also see an explanation of alert(), confirm() and prompt() on the Windows object page.
methods | Description |
---|---|
alert(msg) | Displays an Alert dialog box with the desired message and OK button. |
confirm(msg) | Displays a Confirm dialog box with the specified message and OK and Cancel buttons. Example(s) |
prompt(msg, [input]) | Displays a Prompt dialog box with a message. Optional "input" argument allows you to specify the default input (response) that gets entered into the dialog box. Set "input" to "" to create a blank input field. Example(s) |
Examples
confirm(msg)
var yourstate=window.confirm("Are you sure you are ok?")
if (yourstate) //Boolean variable. Sets to true if user pressed "OK" versus
"Cancel."
window.alert("Good!")
prompt(msg, [input])
var thename=window.prompt("please enter your name")
window.alert(thename)
- JavaScript Operators
- JavaScript Statements
- Global functions
- JavaScript Events
- Escape Sequences
- Reserved Words