Convert array to array of objects with reduce

Question

optimizedRoute = ['Bengaluru', 'Salem', 'Erode', 'Tiruppur', 'Coimbatore']  result = [   {start: bengaluru, end: salem},   {start: salem, end: erode},   {start: erode, end: tiruppur},   {start: tiruppur, end: coimbatore}, ] 

I want to convert optimizedRoute to result. I want to do this with ES6 .reduce(). Here is what I've tried:

const r = optimizedRoute.reduce((places, place, i) => {   const result: any = [];   places = []   places.push({     startPlace: place,     endPlace: place   });   // result.push ({ startplace, endplace, seats: 4 });   // console.log(result);   return places; }, {}); console.log(r) 

Answer 1

You could use reduce for getting start and end part of the route and return the end for the next start.

getParts = a => (                   // take a as array and return an IIFE     r => (                          // with an initialized result array         a.reduce((start, end) => (  // reduce array by taking two values             r.push({ start, end }), // push short hand properties             end                     // and take the last value as start value for next loop         )),         r                           // finally return result     ) )([]);                              // call IIFE with empty array 

const getParts = a => (r => (a.reduce((start, end) => (r.push({ start, end }), end)), r))([]);    var optimizedRoute = ['Bengaluru', 'Salem', 'Erode', 'Tiruppur', 'Coimbatore']    console.log(getParts(optimizedRoute));

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@EDIT Grégory NEUT adding explaination

// Two thing to know first :    // When no initial value is provided,  // Array.reduce takes the index 0 as first value and start to loop at index 1    // Doing (x, y, z)  // Will execute the code x, y and z    // Equivalent to :    // x;  // y;  // z;    let ex = 0;    console.log((ex = 2, ex = 5, ex = 3));    // So about the code    const getParts = (a) => {    // We are creating a new function here so we can have an array where to    // push data to    const func = (r) => {      // Because there is no initial value      //      // Start will be the value at index 0 of the array      // The loop is gonna start at index 1 of the array      a.reduce((start, end) => {        console.log(start, end);          r.push({          start,          end,        });          return end;      });        return r;    };      return func([]);  };    // Equivalent  const getPartsEquivalent = (a) => {    const r = [];      // Because there is no initial value    //    // Start will be the value at index 0 of the array    // The loop is gonna start at index 1 of the array    a.reduce((start, end) => {      console.log(start, end);        r.push({        start,        end,      });        return end;    });      return r;  };    var optimizedRoute = ['Bengaluru', 'Salem', 'Erode', 'Tiruppur', 'Coimbatore']    console.log(getPartsEquivalent(optimizedRoute));

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