Add element conditional between group of objects-CodePudding

I have the following code, to make a new array.

const datos = [{
        "id": "re_alt_sr",
        "quantity": 345,
        "selectable": false
      },
      {
        "id": "re_alt_gen",
        "quantity": 740,
        "selectable": true
      },
      {
        "id": "re2_alw_gen2",
        "quantity": 40,
        "selectable": true
      },
      {
        "id": "re_st_w_show",
        "quantity": 1,
        "selectable": true
      }]
var list = [];
for (const item of datos) {
  list.push({
    name: item.id,
    value: item.quantity,
    is: item.selectable
  })
}

console.log(list)

But I want to add a new element among which are selectable.

{"name": "default", "value": 0, "status": true}

Leaving something like this:

[
    {"name": "re_alt_sr", "value": 345, "is": false },
    {"name": "re2_alw_gen2","value": 40,"is": true },
    {"name": "default", "value": 0, "status": true},
    {"name": "re_alt_gen", "value": 740, "is": true},
    {"name": "default", "value": 0, "status": true},
    {"name": "re_st_w_show", "value": 1, "is": true}
]

Point to clarify: as you think: unselectables are one group and SI-selectables is another. There will be other arrays that are all "unselectable" so you don't need to add anything to them.

CodePudding user response：

This SOLUTION stays close to your existing code by employing an if statement to get the "new element between those that are not selectable and those that are.".

Essentially what it does is keep track of the previous item's selectable state, and when a difference is detected, it inserts the new element.

const datos = [{
        "id": "re_alt_sr",
        "quantity": 345,
        "selectable": false
      },
      {
        "id": "re_alt_gen",
        "quantity": 740,
        "selectable": true
      },
      {
        "id": "re_st_w_show",
        "quantity": 1,
        "selectable": true
      }]
var list = [];

// Var to track of previous item's selectable state
var previousSelectableState = null; 

for (const item of datos) {
    
    
    // NEW CODE BEGIN
    if ( previousSelectableState !== null) {
        // Not at first item    
        
        if (previousSelectableState !== item.selectable ) {
            // Previous item selectable differs from this one
        
            list.push( {"id": "default", "quantity": 0, "status": true} );
        }
    }
    
    previousSelectableState = item.selectable; // for next iteration
    // NEW CODE END
    
    list.push({
        name: item.id,
        value: item.quantity,
        is: item.selectable
    })

}

console.log(list)

CodePudding user response：

You can use .reduce(), which is a useful function that iterates through an array, and passes a value from each iteration to the next.

const datos = [{"id": "re_alt_sr","quantity": 345,"selectable": false},{"id": "re_alt_gen","quantity": 740,"selectable": true},{"id": "re_st_w_show","quantity": 1,"selectable": true}];

const list = datos.reduce((acc, val) => {
  // Can't use index here because we may have already 
  // injected extra items into array. So we use length instead
  const prev = acc[acc.length - 1];
  return prev && prev.selectable !== val.selectable ?
    [
      ...acc,
      {"id": "default", "quantity": 0, "status": true},
      val
    ] : 
    [...acc, val];
},[]);

console.log(list)