Syntax and usage of logical functions in EdgeScript - ApsaraVideo VOD - Alibaba Cloud - ApsaraVideo VOD

and

The following table describes the and function.

Item	Description
Syntax	`and(arg, ...)`
Benefit	Performs a logical AND operation. Supports short-circuit evaluation. If any argument evaluates to false, subsequent arguments are not evaluated.
Parameter	One or more arguments of any type.
Return value	Returns `true` if all values evaluate to true and returns `false` if a value evaluates to false.
Example	`if and($arg_mode, eq($arg_mode, 'set_header')) { add_rsp_header('USER-DEFINED-1','path1') }` a. If the request includes the mode parameter and the value of the mode parameter is set_header, set the USER-DEFINED-1 response header. b. If the request does not include the mode parameter, the short-circuit evaluation takes effect and the eq comparison operator is not executed. The response header USER-DEFINED-1 will not be set because the and() function returns a value of false.

The following table describes the or function.

Item	Description
Syntax	`or(arg, ...)`.
Description	A logical OR operator. Supports short-circuit evaluation. If an argument evaluates to true, subsequent arguments are not evaluated.
Parameter	One or more arguments of any type.
Return value	Returns `true` if any argument is true. Otherwise, returns `false`.
Example	`if and($http_from, or(eq($http_from, 'wap'), eq($http_from, 'comos'))) { rewrite(concat('http://example.com.cn/zt_d/we2015/', $http_from), 'enhance_redirect') }` If the `from` request header exists and its value is either `wap` or `comos`, the request is redirected with a 302 status. The script forms the target URL by concatenating `http://example.com.cn/zt_d/we2015/` and the value of the `from` header. If the `from` request header has the value `wap`, short-circuit evaluation occurs, skipping the subsequent comparison with `comos`. The `or()` function then returns `true`.

The following table describes the not function.

Item	Description
Syntax	`not(arg)`
Description	Performs a logical NOT operation. `undef` and `false` evaluate to false. All other values evaluate to true.
Parameter	One argument of any type.
Return value	true false
Example	`if not($arg_key) { exit(403) } if not($cookie_user) { exit(403, 'not cookie user') } if not(0) { exit(403) } if not(false) { exit(403) }` If a request does not include the key parameter, the request is denied and the HTTP 403 status code is returned. If a request does not include `cookie_user`, the request is denied. The HTTP 403 status code and the response body `"not cookie user"` are returned. The `not(0)` function returns a value of false. The `not(false)` function returns a value of true.

The following table describes the eq function.

Item	Description
Syntax	`eq(arg1, arg2)`
Description	Checks whether two values are equal.
Parameter	arg1: the first value to compare. Data type: any type. arg2: the second value to compare. Data type: same as the `arg1` parameter.
Return value	Returns `true` if the two values are equal and returns `false` if they are not equal.
Example	`key1 = 'value1' key2 = 'value2' if and($arg_k1, $arg_k2, eq(key1, $arg_k1), ne(key2, $arg_k2)) { say('match condition') }` a. If the request includes both the k1 and k2 parameters, the comparison operations are performed. b. If the request does not include the k1 or k2 parameter, the short-circuit evaluation takes effect and the comparison operations are not performed. eq: c. eq: whether the value of the k1 parameter is equal to value1. ne: d. ne: whether the value of the k2 parameter is not equal to value2. e. The response that contains the response body "match condition" is returned only if the following conditions are met: the request includes both the k1 and k2 parameters, the value of the k1 parameter is equal to value1, and the value of the k2 parameter is not equal to value2.

The following table describes the ne function.

Item	Description
Syntax	`ne(arg1, arg2)`
Description	Checks whether two values are not equal.
Parameter	arg1: the first value to compare. Data type: any type. arg2: the second value to compare. Data type: same as the `arg1` parameter.
Return value	Returns `true` if the two values are not equal and returns `false` if they are equal.
Example	`key1 = 'value1' key2 = 'value2' if and($arg_k1, $arg_k2, eq(key1, $arg_k1), ne(key2, $arg_k2)) { say('match condition') }` a. If the request includes both the k1 and k2 parameters, the comparison operations are performed. b. If the request does not include the k1 or k2 parameter, the short-circuit evaluation takes effect and the comparison operations are not performed. eq: c. eq: whether the value of the k1 parameter is equal to value1. ne: d. ne: whether the value of the k2 parameter is not equal to value2. e. The response that contains the response body "match condition" is returned only if the following conditions are met: the request includes both the k1 and k2 parameters, the value of the k1 parameter is equal to value1, and the value of the k2 parameter is not equal to value2.

The following table describes the null function.

Item	Description
Syntax	`null(v)`
Benefit	Checks whether a data type is specified for EdgeScript (ES).
Filed	v: the parameter to pass. Data type: array, dictionary, or string. A value of false is returned for other data types.
Return value	Data type: Boolean. A value of true is returned if the value of v is an array or a dictionary. A value of true is returned if the value of v is an empty string. A value of false is returned if v is set to other data types.
Examples	`d = [] say(null(d)) set(d, 1, 'v1') say(null(d)) say(tostring(null('x'))) say(tostring(null('')))` Output: `true false false true`