[GitHub] [arrow] domoritz opened a new pull request #10339: ARROW-12799: [JS] Use Nullish Coalescing Operator (??) For Defaults

[GitBox <gi...@apache.org>]

domoritz opened a new pull request #10339:
URL: https://github.com/apache/arrow/pull/10339


   **The nullish coalescing operator (`??`) returns its right side when its left side is nullish** (`null` or `undefined`), and its left side otherwise.
   For example, `const x = a ?? b` would set `x` to `a` if `a` has a value, and to `b` if `a` is `null` or `undefined`.
   
   The nullish coalescing operator is very useful to **provide default values when a value or an expression is nullish**.
   Before its introduction in ES2020, this default value pattern was often expressed using the conditional operator.
   
   This refactoring simplifies conditional (ternary) checks to nullish coalescing operator expressions:
   
   * `a == null ? x : a` becomes `a ?? x`
   * `a != null ? a : x` becomes `a ?? x`
   * `a === null || a === undefined ? x : a` becomes `a ?? x`
   * `a !== null && a !== undefined ? a : x` becomes `a ?? x`
   * `f(1) != null ? f(1) : x` becomes `f(1) ?? x`
   * etc.
   
   Learn More: [Nullish coalescing operator (MDN)](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Nullish_coalescing_operator)
   
   When two similar-looking function calls have a side effect, this refactoring can change the behavior of the code.
   
   For example, the refactoring changes:
   
   ```javascript
   let a = f(1) === null || f(1) === undefined ? 'default' : f(1);
   ```
   
   into
   
   ```javascript
   let a = f(1) ?? 'default';
   ```
   
   If `f(1)` has a side effect, it would have been called one, two or three times before the refactoring, and once after the refactoring.
   This means that the side effect would have been called a different number of times, potentially changing the behavior.


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[GitHub] [arrow] domoritz closed pull request #10339: ARROW-12799: [JS] Use Nullish Coalescing Operator (??) For Defaults

[GitBox <gi...@apache.org>]

domoritz closed pull request #10339:
URL: https://github.com/apache/arrow/pull/10339


   


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[GitHub] [arrow] github-actions[bot] commented on pull request #10339: ARROW-12799: [JS] Use Nullish Coalescing Operator (??) For Defaults

[GitBox <gi...@apache.org>]

github-actions[bot] commented on pull request #10339:
URL: https://github.com/apache/arrow/pull/10339#issuecomment-841696000


   https://issues.apache.org/jira/browse/ARROW-12799


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[GitHub] [arrow] domoritz closed pull request #10339: ARROW-12799: [JS] Use Nullish Coalescing Operator (??) For Defaults

[GitBox <gi...@apache.org>]

domoritz closed pull request #10339:
URL: https://github.com/apache/arrow/pull/10339


   


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