Reduces an array to a single value
Device + Agent
| Name | Type | Description |
|---|---|---|
| function | Function |
A reduction function
|
Any Squirrel data type
This method applies the supplied function to all of the items in the target array, starting with the first two. The function returns a single value which is then combined with the next (third) item in the array — and so on until all of the items have been combined into a single value which the method returns.
The reduction function must include two parameters: the result returned by its previous iteration and the next item in the array — reduce() takes care of iterating through the target array’s items.
If the target array contains just a single item, that item will be the value that is returned. If the target contains no items, reduce() will return null.
The example below shows the use of reduce() to add the elements of the array sourceArray. The function used to perform the reduction can be simplified further if we use a Squirrel lambda function, and this is shown in the second example.
The third example shows how reduce() can be used on an array of string segments (generated by splitting a source string into sub-strings separated by a newline) to reassemble the string after processing.
| local sourceArray = [10, 21, 30, 43]; | |
| // Combine all the values in the array | |
| local reduction = sourceArray.reduce(function(previousValue, currentValue){ | |
| return (previousValue + currentValue); | |
| }); | |
| server.log(reduction); | |
| // Displays "104" |
| local sourceArray = [10, 21, 30, 43]; | |
| // Combine all the values in the array | |
| local reduction = sourceArray.reduce(@(p, c) p + c); | |
| server.log(reduction); | |
| // Displays "104" |
| // Decode an X.509 certificate .pem file | |
| // Remove the armor, concatenate the lines and base64 decode the text | |
| function decodePem(pemString) { | |
| local lines = split(pemString, "\n"); | |
| // We really ought to iterate over the array until we find a starting line, | |
| // and then look for the matching ending line, rather than assuming its on line 0 | |
| if ((lines[0] == "-----BEGIN PRIVATE KEY-----" && | |
| lines[lines.len() - 1] == "-----END PRIVATE KEY-----") || | |
| (lines[0] == "-----BEGIN RSA PRIVATE KEY-----" && | |
| lines[lines.len() - 1] == "-----END RSA PRIVATE KEY-----") || | |
| (lines[0] == "-----BEGIN PUBLIC KEY-----" && | |
| lines[lines.len() - 1] == "-----END PUBLIC KEY-----")) { | |
| local all = lines.slice(1, lines.len() - 1).reduce(@(a, b) a + b); | |
| return http.base64decode(all); | |
| } | |
| return null; | |
| } |