Syntax, Parameter and Return Value
Syntax:
_.rest(func, [start=func.length-1])
Parameters:
-
func (Function): The function to apply the rest parameter to.
- [start=func.length-1] (number): The position at which to start collecting arguments.
Return Value:
(Function) - Returns the new function.
Examples
Collecting Additional Arguments:
JavaScript
var _ = require('lodash');
function assembleMessage(firstWord, ...restWords) {
return firstWord + ' ' + restWords.join(' ');
}
var enhancedAssembleMessage = _.rest(assembleMessage);
console.log(enhancedAssembleMessage('Hello', 'world', 'from', 'Lodash!'));
You can also try this code with Online Javascript Compiler
Output:
'Hello world from Lodash!'
Demonstrates collecting all arguments beyond the first into an array.
Creating Variadic Functions:
JavaScript
function sum(...numbers) {
return numbers.reduce((total, n) => total + n, 0);
}
var variadicSum = _.rest(sum, 2);
console.log(variadicSum(1, 2, 3, 4));
You can also try this code with Online Javascript Compiler
Output:
9 (sum of 2, 3, 4)
Shows creating a function that sums all arguments after the first two.
Handling Event Listeners:
JavaScript
function handleEvent(eventType, ...details) {
console.log(`Event: ${eventType}, Details:`, details);
}
var enhancedHandleEvent = _.rest(handleEvent);
enhancedHandleEvent('click', 'button1', 'header', 'footer');function handleEvent(eventType, ...details) {
console.log(`Event: ${eventType}, Details:`, details);
}
var enhancedHandleEvent = _.rest(handleEvent);
enhancedHandleEvent('click', 'button1', 'header', 'footer');
You can also try this code with Online Javascript Compiler
Output:
'Event: click, Details: ['button1', 'header', 'footer']'
An example of using _.rest() to handle variadic arguments in event listeners.
Processing Command-Line Arguments:
JavaScript
function processCommands(command, ...options) {
console.log(`Command: ${command}, Options:`, options);
}
var processCommandsVariadic = _.rest(processCommands);
processCommandsVariadic('start', '--verbose', '--timeout=20');
You can also try this code with Online Javascript Compiler
Output:
'Command: start, Options: ['--verbose', '--timeout=20']'
Demonstrates processing a list of command-line arguments.
Frequently Asked Questions
How is _.rest() different from native JavaScript rest parameters?
_.rest() is similar to native JavaScript rest parameters but offers more control, allowing you to specify from which argument to start collecting the rest of the arguments.
Can _.rest() be used with functions of any arity?
Yes, _.rest() can be used with functions of any arity. It's particularly effective with functions where the number of arguments isn't fixed.
Is the original function modified by _.rest()?
No, _.rest() creates a new function and does not modify the original function. The original function remains as it is.
Conclusion
Lodash's _.rest() method offers a convenient way to handle variadic functions, allowing for the easy grouping of arguments beyond a certain point. It's a useful tool for functions that need to process an indefinite number of arguments or need to operate on the latter part of their arguments.
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