JavaScript iri-iri : Fahimtar rage aiki

ginin kalma

arr.reduce(callbackFunction, [initialValue])

Menene Rage yi?

Rage ne mai aiki da madaukai ta hanyar wani tsararru.

Ayyuka za a iya yi a kan tsararru via wani callback aiki.

A karshen ayyukan a kan tsararru, rage ya dawo guda darajar

Rage za a iya amfani da, misali, to total wani Siyayya

misali

  bari arr = [1,2,3,4,5];
  arr.reduce( (accumulator, currentValue, currentIndex, tsararru) => { 
      //wasu ayyukan;
      komawa wani abu;
  });

 

The Callback Function

The callback function is invoked for each element in the array, passing in 4 arguments which are passed in by the reduce function.

These 4 arguments then can be used in our callback function.

Takes four arguments

1. accumulator – The first element of the array on the first loop or initial value if supplied. Then the returned value of the previous loop.
2. currentValue – A halin yanzu kashi a cikin tsararru. Starts from the second element in the array ie. arr[1], when the initial value argument is not passed. If the initial value argument is passed then current value starts from the 1st element in the array arr[0].
3. currentIndex – A index of yanzu kashi.
4. tsararru – A dukan tsararru.

Working Example

bari arr = [1,2,3,4,5];

arr.reduce(
  (accumulator, currentValue, currentIndex, tsararru) => {
    console.log(`accumulator (On 1st loop, accumulator is arr[0], then it is the returned value of the previous loop): ${accumulator}`);
    console.log(`currentValue (Loops through the array, starting at arr[1]): ${currentValue}`);
    console.log(`currentIndex: ${currentIndex}`);
    console.log(`tsararru: ${tsararru}`);
    console.log('---');
    samu accumulator + currentValue;
  }
);

Output

accumulator (On 1st loop, accumulator is arr[0], then it is the returned value of the previous loop): 1
currentValue (Loops through the array, starting at arr[1]): 2
currentIndex: 1
tsararru: 1,2,3,4,5
---
accumulator (On 1st loop, accumulator is arr[0], then it is the returned value of the previous loop): 3
currentValue (Loops through the array, starting at arr[1]): 3
currentIndex: 2
tsararru: 1,2,3,4,5
---
accumulator (On 1st loop, accumulator is arr[0], then it is the returned value of the previous loop): 6
currentValue (Loops through the array, starting at arr[1]): 4
currentIndex: 3
tsararru: 1,2,3,4,5
---
accumulator (On 1st loop, accumulator is arr[0], then it is the returned value of the previous loop): 10
currentValue (Loops through the array, starting at arr[1]): 5
currentIndex: 4
tsararru: 1,2,3,4,5
---

 

Samar da farko darajar

Tantance na biyu siga (initialValue) a rage aiki zai haifar da initialValue da za a wuce a matsayin accumulator shaida a kan na farko madauki.

Ka lura da cewa a halin yanzu darajar a kan 1st madauki yanzu yana farawa a farko kashi na tsararru

Working Example

  bari arr = [1,2,3,4,5];

  arr.reduce(
  (accumulator, currentValue, currentIndex, tsararru) => {
    console.log(`accumulator ( A cikin 1st madauki, wannan shi ne na farko da darajar, sa'an nan suka komo daga darajar baya madauki): ${accumulator}`);
    console.log(`currentValue (Loops through the array, starting at arr[0]): ${currentValue}`);
    console.log(`currentIndex: ${currentIndex}`);
    console.log(`tsararru: ${tsararru}`);
    console.log('---');
    samu accumulator + currentValue;
  }, 0
);

Output

accumulator ( A cikin 1st madauki, wannan shi ne na farko da darajar, sa'an nan suka komo daga darajar baya madauki): 0
currentValue (Loops through the array, starting at arr[0]): 1
currentIndex: 0
tsararru: 1,2,3,4,5
---
accumulator ( A cikin 1st madauki, wannan shi ne na farko da darajar, sa'an nan suka komo daga darajar baya madauki): 1
currentValue (Loops through the array, starting at arr[0]): 2
currentIndex: 1
tsararru: 1,2,3,4,5
---
accumulator ( A cikin 1st madauki, wannan shi ne na farko da darajar, sa'an nan suka komo daga darajar baya madauki): 3
currentValue (Loops through the array, starting at arr[0]): 3
currentIndex: 2
tsararru: 1,2,3,4,5
---
accumulator ( A cikin 1st madauki, wannan shi ne na farko da darajar, sa'an nan suka komo daga darajar baya madauki): 6
currentValue (Loops through the array, starting at arr[0]): 4
currentIndex: 3
tsararru: 1,2,3,4,5
---
accumulator ( A cikin 1st madauki, wannan shi ne na farko da darajar, sa'an nan suka komo daga darajar baya madauki): 10
currentValue (Loops through the array, starting at arr[0]): 5
currentIndex: 4
tsararru: 1,2,3,4,5
---