Map Filter Reduce

• higher order methods

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Map

• creates a new array by performing some action on each element
  • forEach does not do this , but you can just iterate though it
  • let a = num.forEach is not possible
  • Copy

      // Map Filter Reduce - higher order methos
      let arr = [45 , 23 , 44]
      console.log(arr)
      // Array Map method
      // .map creates new array .forEach modifies the same array
      let newarr = arr.map((value,index,array)=> {
          console.log(value,index,array) // index and array are optional args
          return value*value
      })
      console.log(newarr)
    

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Filter

• • Does some filtering based on a function and makes new array
  • Copy

      // Filter
      let arr2 = [0,3,5,45,56,78]
      let newarr2 = arr2.filter((value)=> {
          return value<10
      })
      console.log(newarr2)
    

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Reduce

• Traverses through the array and returns smaller dimesion value
• Copy

   // Reduce method
   let arr3  = [0,3,5,4,6,7]
   let newarr3 = arr3.reduce((value1,value2)=> {
       return value1 + value2
   // it takes first two values and runs the function and takes the output and runs on 3 element and continues
   })
   console.log(newarr3)
   const sum = (a,b) => {
       return a + b
   }
   console.log(arr3.reduce(sum)) // same as giving function inside