How to use JavaScript's reduce ()
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Case study
Calculate the sum of the added elements of the array:
Varnumbers= [65,44,12,4]
FunctiongetSum (total,num) {
Returntotal+num
}
FunctionmyFunction (item) {
Document.getElementById ("demo") [xss_clean] = numbers.reduce (getSum)
}
Output result:
one hundred and twenty five
Definition and usage
The reduce () method takes a function as an accumulator, and each value in the array (from left to right) starts to shrink and eventually evaluates to a value.
Reduce () can be used as a higher-order function for the compose of a function.
Note: reduce () does not execute callback functions for empty arrays.
Browser support
The numbers in the table represent the first browser version number that supports the method.
Method
Reduce () Yes 9.03.04 10.5
Grammar.
Array.reduce (function (total,currentValue,currentIndex,arr), initialValue)
Parameters.
Parameter description
Function (total,currentValue,index,arr) is required. The function used to execute each array element.
Function parameters:
Parameter description
Total is required. The initial value, or the return value after the calculation is finished.
CurrentValue is required. Current element
CurrentIndex is optional. Index of the current element
Arr is optional. The array object to which the current element belongs.
InitialValue is optional. The initial value passed to the function
Technical details
Return value: returns the calculation result
JavaScript version: ECMAScript3
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