Constants
(constant) Infinity :number
The name
Infinity refers to the special number value Infinity.
See ECMAScript Specification, Section 4.3.23
Type:
- number
(constant) NaN :number
The name
NaN refers to the special number value NaN ("not a number"). Note that
NaN is a number, as specified by is_number.
See ECMAScript Specification, Section 4.3.24
Type:
- number
(constant) undefined :undefined
The name
undefined refers to the special value undefined.
See also textbook explanation in section 4.1.1.
Type:
Functions
arity(f) → {number}
Returns the number of parameters the given function
f expects,
excluding the rest parameter.
Parameters:
| Name | Type | Description |
|---|---|---|
f |
function | given function |
Returns:
number of parameters f expects
- Type
- number
char_at(s, i) → {string}
Takes a string
s as first argument and a nonnegative integer
i as second argument. If i is less than the length
of s, this function returns a one-character string that contains
the character of s at position i, counting from 0.
If i is larger than or equal to the length of
s, this function returns undefined.
Parameters:
| Name | Type | Description |
|---|---|---|
s |
string | given string |
i |
number | index |
Returns:
one-character or undefined
- Type
- string
display(v, s) → {value}
Optional second argument. If present,
displays the given string
s, followed by a space character, followed by the
value v in the console.
If second argument not present,
just displays the value v in the console.
The notation used for the display of values
is consistent with
JSON,
but also displays undefined, NaN, Infinity, and function objects.
Parameters:
| Name | Type | Description |
|---|---|---|
v |
value | to be displayed |
s |
string | to be displayed, preceding v, optional argument |
Returns:
v, the first argument value
- Type
- value
error(v, s)
Optional second argument.
If present,
displays the given string
s, followed by a space character, followed by the
value v in the console with error flag.
If second argument not present,
just displays the value v in the console with error flag.
The evaluation
of any call of error aborts the running program immediately.
The notation used for the display of values
is consistent with
JSON,
but also displays undefined, NaN, Infinity, and function objects.
Parameters:
| Name | Type | Description |
|---|---|---|
v |
value | to be displayed |
s |
string | to be displayed, preceding v |
get_time() → {number}
Returns number of milliseconds elapsed since January 1, 1970 00:00:00 UTC.
See also textbook example.
Returns:
current time in milliseconds
- Type
- number
is_boolean(v) → {boolean}
checks whether a given value is a boolean
Parameters:
| Name | Type | Description |
|---|---|---|
v |
value | to be checked |
Returns:
indicating whether the value is a boolean
- Type
- boolean
is_function(v) → {boolean}
checks whether a given value is a function
Parameters:
| Name | Type | Description |
|---|---|---|
v |
value | to be checked |
Returns:
indicating whether the value is a function
- Type
- boolean
is_number(v) → {boolean}
checks whether a given value is a number.
See also textbook example.
Parameters:
| Name | Type | Description |
|---|---|---|
v |
value | to be checked |
Returns:
indicating whether the value is a number
- Type
- boolean
is_string(v) → {boolean}
checks whether a given value is a string.
See also textbook example.
Parameters:
| Name | Type | Description |
|---|---|---|
v |
value | to be checked |
Returns:
indicating whether the value is a string
- Type
- boolean
is_undefined(v) → {boolean}
checks whether a given value is the special value
undefined
Parameters:
| Name | Type | Description |
|---|---|---|
v |
value | to be checked |
Returns:
indicating whether the value is
undefined
- Type
- boolean
parse_int(s, i) → {number}
Interprets a given string
Examples:
See ECMAScript Specification, Section 18.2.5 for details.
s as an integer,
using the positive integer i as radix,
and returns the respective value.
Examples:
parse_int("909", 10) returns the number
909, and parse_int("-1111", 2) returns the number
-15.See ECMAScript Specification, Section 18.2.5 for details.
Parameters:
| Name | Type | Description |
|---|---|---|
s |
string | string to be converted |
i |
number | radix |
Returns:
result of conversion
- Type
- number
prompt(s) → {string}
Pops up a window that displays the string
s, provides
an input line for the user to enter a text, a Cancel button and an OK button.
The call of prompt
suspends execution of the program until one of the two buttons is pressed. If
the OK button is pressed, prompt returns the entered text as a string.
If the Cancel button is pressed, prompt returns a non-string value.
Parameters:
| Name | Type | Description |
|---|---|---|
s |
string | to be displayed in popup |
Returns:
entered text
- Type
- string
stringify(v) → {string}
returns a string that represents the value
v, using a
notation that is is consistent with
JSON,
but also displays undefined, NaN, Infinity, and function objects.
See also textbook example.
Parameters:
| Name | Type | Description |
|---|---|---|
v |
value | the argument value |
Returns:
string representation of v
- Type
- string