Syntax, Parameter and Return Value
Syntax:
_.rearg(func, indexes)
Parameters:
-
func (Function): The function to rearrange arguments for.
- indexes (Array|number): The arranged indexes of arguments.
Return Value:
(Function) - Returns the new function with rearranged argument order.
Examples
Swapping Arguments of a Function:
JavaScript
var _ = require('lodash');
function divide(a, b) {
return a / b;
}
var flippedDivide = _.rearg(divide, [1, 0]);
console.log(flippedDivide(2, 10));
You can also try this code with Online Javascript Compiler
Output:
5 (10 / 2)
Demonstrates swapping the order of arguments for a division function.
Reordering Arguments for Compatibility:
JavaScript
function log(level, message, date) {
console.log(`[${date}] [${level}]: ${message}`);
}
var reorderedLog = _.rearg(log, [2, 0, 1]);
reorderedLog('INFO', 'Log message', new Date().toISOString());
You can also try this code with Online Javascript Compiler
// Rearranges to put the date first, followed by level and message
Shows reordering arguments to fit a specific logging format.
Adjusting Argument Order for Event Handlers:
JavaScript
function customEventHandler(arg1, event) {
console.log(`Event type: ${event.type}, Data: ${arg1}`);
}
var eventHandler = _.rearg(customEventHandler, [1, 0]);
document.addEventListener('click', event => eventHandler('Click data', event));
You can also try this code with Online Javascript Compiler
// Properly orders arguments for the event handler
An example of reordering arguments for an event handler function.
Function Adaptation for Array Methods:
JavaScript
function startsWith(prefix, string) {
return string.startsWith(prefix);
}
var checkStartsWith = _.rearg(startsWith, [1, 0]);
var words = ['apple', 'banana', 'avocado'];
var aWords = _.filter(words, _.partial(checkStartsWith, 'a'));
console.log(aWords);
You can also try this code with Online Javascript Compiler
Output:
['apple', 'avocado']
Demonstrates reordering a predicate function for use with _.filter.
Frequently Asked Questions
Can _.rearg() handle functions with multiple arguments?
Yes, _.rearg() is designed to handle functions with multiple arguments, allowing you to reorder them as needed.
How does _.rearg() differ from simply wrapping a function?
While you can wrap a function to reorder arguments, _.rearg() provides a more concise and declarative way to achieve this, especially for simple reordering needs.
Is the original function modified by _.rearg()?
No, _.rearg() creates a new function without altering the original function. The original function remains available with its original argument order.
Conclusion
Lodash's _.rearg() method is a practical tool for rearranging the order of arguments passed to a function. It offers a flexible way to adapt and interface with existing functions, enhancing compatibility and easing integration with different codebases or APIs.
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