javascript - Assignment to property of function parameter 'a' Eslint - Stack Overflow

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I am trying to sort array of object with custom function.
So, I define my function

   sortingAlgo = (a, b) => {
        // we need to use custom sorting algorithm to meet our requirements.
        a.pos = a.pos.toUpperCase();
        b.pos = b.pos.toUpperCase();
        if(a.pos.slice(0, 1) === b.pos.slice(0, 1)) {
          if (parseInt(a.pos.slice(1)) < parseInt(b.pos.slice(1))){
            return -1;
          }
          if (parseInt(a.pos.slice(1)) > parseInt(b.pos.slice(1))){
            return 1;
          }
          return 0;
        } else {
          if (parseInt(a.pos.slice(0, 1)) < parseInt(b.pos.slice(0, 1))){
            return -1;
          }
          if (parseInt(a.pos.slice(0, 1)) > parseInt(b.pos.slice(0, 1))){
            return 1;
          }
          return 0;

        }
      }

And i call it like this.

const sortedProducts = data.data.sort(this.sortingAlgo);

Now i Got Eslint error saying.

**

• 169:5 error Assignment to property of function parameter 'a' no-param-reassign
• 170:5 error Assignment to property of function parameter 'b' no-param-reassign

**

I searched and found that this rule is set byt airBnB. So i dont think its right to disable this rule.
So can somebody tell me how to resolve it or if disabling this rule is okay.

I am trying to sort array of object with custom function.
So, I define my function

   sortingAlgo = (a, b) => {
        // we need to use custom sorting algorithm to meet our requirements.
        a.pos = a.pos.toUpperCase();
        b.pos = b.pos.toUpperCase();
        if(a.pos.slice(0, 1) === b.pos.slice(0, 1)) {
          if (parseInt(a.pos.slice(1)) < parseInt(b.pos.slice(1))){
            return -1;
          }
          if (parseInt(a.pos.slice(1)) > parseInt(b.pos.slice(1))){
            return 1;
          }
          return 0;
        } else {
          if (parseInt(a.pos.slice(0, 1)) < parseInt(b.pos.slice(0, 1))){
            return -1;
          }
          if (parseInt(a.pos.slice(0, 1)) > parseInt(b.pos.slice(0, 1))){
            return 1;
          }
          return 0;

        }
      }

And i call it like this.

const sortedProducts = data.data.sort(this.sortingAlgo);

Now i Got Eslint error saying.

**

• 169:5 error Assignment to property of function parameter 'a' no-param-reassign
• 170:5 error Assignment to property of function parameter 'b' no-param-reassign

**

I searched and found that this rule is set byt airBnB. So i dont think its right to disable this rule.
So can somebody tell me how to resolve it or if disabling this rule is okay.

• javascript
• reactjs
• eslint

Share Improve this question Follow asked Feb 24, 2019 at 5:52 Rajan LagahRajan Lagah 2,52811 gold badge2626 silver badges4646 bronze badges

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2 Answers 2

Sorted by: Reset to default 3

There's no need to reassign the pos property of the function arguments (a, b). You should just assign a new variable (aPos, bPos), which is a best practice, hence why ESLint is plaining.

You should avoid unnecessary mutations/side-effects whenever possible in your code to prevent bugs and create an overall more efficient program architecture.

More specifically in this case..

ESLint: Disallow Reassignment of Function Parameters (no-param-reassign)

const sortingAlgo = (a, b) => {
    // we need to use custom sorting algorithm to meet our requirements.
    let aPos = a.pos.toUpperCase(),
        bPos = b.pos.toUpperCase();

    if (aPos.slice(0, 1) === bPos.slice(0, 1)) {
        if (parseInt(aPos.slice(1)) < parseInt(bPos.slice(1))) {
            return -1;
        }
        if (parseInt(aPos.slice(1)) > parseInt(bPos.slice(1))) {
            return 1;
        }
        return 0;
    } else {
        if (parseInt(aPos.slice(0, 1)) < parseInt(bPos.slice(0, 1))) {
            return -1;
        }
        if (parseInt(aPos.slice(0, 1)) > parseInt(bPos.slice(0, 1))) {
            return 1;
        }
        return 0;

    }
}

You ESLint is configured to not allow re-assignment of parameters, i.e if a function takes 2 arguments (a, b), then you CANT re-assign these 2 variables in the function body.

To fix this error, either:

• disable the eslint rule (in your .eslintrc or just for the function)
• create new variables to avoid re-assigning to a and b (see below):

 sortingAlgo = (a, b) => {
        // we need to use custom sorting algorithm to meet our requirements.
        const aPos = a.pos.toUpperCase();
        const bPos = b.pos.toUpperCase();
        ...

Then replace references to a.pos and b.pos to aPos and bPos.

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