Ignore verification of unused parameters

Question

Ignore verification of unused parameters

In my typescript project compilation process, I make use of the noImplicitAny option to ensure that I specify the types for variables and arguments.

However, there are instances where I have unused arguments. For instance:

jQuery.ajaxTransport("+*", function (options: JQueryAjaxSettings) {
  return {
    abort: function (_, callback: JQueryCallback) {

For the first argument of the abort function that I am not interested in, I choose to name it as _ to indicate its insignificance.

I wonder if this is the correct approach in TypeScript, as I couldn't find concrete guidelines on it. My suspicion arises from the fact that only one argument can be named _.

Upon compiling, Typescript displays the error:

error TS7006: Parameter '_' implicitly has an 'any' type.

To resolve this, I could simply type _:any, but it seems excessive for an unused argument.

typescript unused-variables

Answer 1

Answer №1

I encountered a similar issue where I only needed the res parameter when working with express and routing.

router.get('/', function (req, res) { res.end('Bye.'); });

Your method of using '_' is effective, but I have also found success in utilizing this approach as well.

function (_1, _2, _3, onlyThis) { console.log(onlyThis); }

This alternative seems more clear, as solely using '_' could potentially lead to confusion with lodash/underscore usage, and it explicitly highlights that your focus is on the 4th parameter.

Update: It's been a while since I initially shared this solution, and there have been some misconceptions in the comments. Therefore, I wanted to provide further clarification.

The underscore trick remains valuable in Typescript. As mentioned earlier, for instance, when employing express and writing app.get('/', (req, res) => {, a warning 'req' is declared but its value is never read will be displayed. However, by changing it to app.get('/', (_req, res) => {, the warning disappears. You should not encounter the

error TS7006: Parameter 'req' implicitly has an 'any' type.

error, as @types/express typically handles the typing for this parameter automatically.

Update 2: The other solution presented here involving {} for parameters may seem stylish, but it significantly impacts speed. Personally, I advise caution when using it within intensive loops.

Answer 2

I encountered a similar issue where I only needed the res parameter when working with express and routing.

router.get('/', function (req, res) { res.end('Bye.'); });

Your method of using '_' is effective, but I have also found success in utilizing this approach as well.

function (_1, _2, _3, onlyThis) { console.log(onlyThis); }

This alternative seems more clear, as solely using '_' could potentially lead to confusion with lodash/underscore usage, and it explicitly highlights that your focus is on the 4th parameter.

Update: It's been a while since I initially shared this solution, and there have been some misconceptions in the comments. Therefore, I wanted to provide further clarification.

The underscore trick remains valuable in Typescript. As mentioned earlier, for instance, when employing express and writing app.get('/', (req, res) => {, a warning 'req' is declared but its value is never read will be displayed. However, by changing it to app.get('/', (_req, res) => {, the warning disappears. You should not encounter the

error TS7006: Parameter 'req' implicitly has an 'any' type.

error, as @types/express typically handles the typing for this parameter automatically.

Update 2: The other solution presented here involving {} for parameters may seem stylish, but it significantly impacts speed. Personally, I advise caution when using it within intensive loops.

Answer 3

Answer №2

Although I may be arriving late to the party, after trying various solutions, I have found one that consistently works for me:

function ({}={}, {}={}, {}={}, onlyThis) { console.log(onlyThis); }

comparison

While experimenting with solutions like _0, _1, ... I encountered issues with nested functions such as:

function parent(_0, _1, _2) {
  function child(_0, _1, _2) {
    // TypeScript being unhappy about shadowed variables
  }
}

However, using empty objects proved to work seamlessly:

function parent({}, {}, {}) {
  function child({}, {}, {}) {
    // :-)
  }
}

Even when specifying the parameter types like:

function parent({}: number, {}: string, {}: any) {
  function child({}: number, {}: string, {}: any) {
    // :-) x2
  }
}

UPDATE:

Additionally, as mentioned here, assigning default values prevents errors from occurring if the provided parameter is undefined or null.

function parent({}={}, {}={}, {}={}) {
  function child({}={}, {}={}, {}={}) {
    // :-)
  }
}

Answer 4

Although I may be arriving late to the party, after trying various solutions, I have found one that consistently works for me:

function ({}={}, {}={}, {}={}, onlyThis) { console.log(onlyThis); }

comparison

While experimenting with solutions like _0, _1, ... I encountered issues with nested functions such as:

function parent(_0, _1, _2) {
  function child(_0, _1, _2) {
    // TypeScript being unhappy about shadowed variables
  }
}

However, using empty objects proved to work seamlessly:

function parent({}, {}, {}) {
  function child({}, {}, {}) {
    // :-)
  }
}

Even when specifying the parameter types like:

function parent({}: number, {}: string, {}: any) {
  function child({}: number, {}: string, {}: any) {
    // :-) x2
  }
}

UPDATE:

Additionally, as mentioned here, assigning default values prevents errors from occurring if the provided parameter is undefined or null.

function parent({}={}, {}={}, {}={}) {
  function child({}={}, {}={}, {}={}) {
    // :-)
  }
}

Answer 5

Answer №3

While this may seem somewhat sacrilegious, here's a snippet you might find useful:

function test(...[,,,value]){
  console.log(value)
}
test(1,2,3,4) //outputs: 4

Answer 6

While this may seem somewhat sacrilegious, here's a snippet you might find useful:

function test(...[,,,value]){
  console.log(value)
}
test(1,2,3,4) //outputs: 4

Ignore verification of unused parameters

Answer №1

Answer №2

comparison

Answer №3

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