Issue: The data type '[number] | [number, number, number, number]' cannot be matched with the type '[number]'

Question

Issue: The data type '[number] | [number, number, number, number]' cannot be matched with the type '[number]'

Upon upgrading from angular 5.1 to 6.1, I started encountering errors in my code, such as the one below:

Error: ngc compilation failed: components/forms/utils.ts(5,3): error TS2322: Type '[number] | [number, number, number, number]' is not assignable to type '[number]'.

Here is the relevant code snippet:

export function bsColumnClass(sizes: [number]) {

  let sizebs = ['col-xs-', 'col-sm-', 'col-md-', 'col-lg-',];

  sizes = sizes || [12, 12, 12, 12];

  let className = sizes.map(function callback(value, index, array) {
    return sizebs[index].concat(value.toString());
  }).join(" ");

  return className;
}

I've identified that the issue lies with the function parameter sizes: [number], and specifically this line of code:

sizes = sizes || [12, 12, 12, 12];

Could you suggest a better approach to resolving this problem?

angular typescript

Answer 1

Answer №1

When coding in Typescript, arrays are typically declared as shown below:

type[]

Instead of using:

[type]

If you make these adjustments to your code, it should function correctly. However, I want to confirm - are you attempting to assign a list of numbers to the 'sizes' variable in case 'sizes' is undefined?

If this is the case, then you should specify the function like so:

function bsColumnClass(sizes?: number[]) {
}

The use of ? ensures that even if no variable is provided to the function, the code remains statically typed and can accept a variable argument.

Answer 2

When coding in Typescript, arrays are typically declared as shown below:

type[]

Instead of using:

[type]

If you make these adjustments to your code, it should function correctly. However, I want to confirm - are you attempting to assign a list of numbers to the 'sizes' variable in case 'sizes' is undefined?

If this is the case, then you should specify the function like so:

function bsColumnClass(sizes?: number[]) {
}

The use of ? ensures that even if no variable is provided to the function, the code remains statically typed and can accept a variable argument.

Answer 3

Answer №2

To specify an array of numbers, you would use the syntax number[] (typically for arrays we use type[]). What you are actually defining is a tuple type, which consists of a fixed number of elements and can have different types of elements.

export function bsColumnClass(sizes: number[]) {


}

If you want to require the caller to provide exactly 4 elements in the array, which seems appropriate in this scenario where sizebs is constant, you can utilize a tuple type:

export function bsColumnClass(sizes: [number, number, number, number]) {

  let sizebs = ['col-xs-', 'col-sm-', 'col-md-', 'col-lg-',];

  sizes = sizes || [12, 12, 12, 12];

  let className = sizes.map(function callback(value, index, array) {
    return sizebs[index].concat(value.toString());
  }).join(" ");

  return className;
}

Answer 4

To specify an array of numbers, you would use the syntax number[] (typically for arrays we use type[]). What you are actually defining is a tuple type, which consists of a fixed number of elements and can have different types of elements.

export function bsColumnClass(sizes: number[]) {


}

If you want to require the caller to provide exactly 4 elements in the array, which seems appropriate in this scenario where sizebs is constant, you can utilize a tuple type:

export function bsColumnClass(sizes: [number, number, number, number]) {

  let sizebs = ['col-xs-', 'col-sm-', 'col-md-', 'col-lg-',];

  sizes = sizes || [12, 12, 12, 12];

  let className = sizes.map(function callback(value, index, array) {
    return sizebs[index].concat(value.toString());
  }).join(" ");

  return className;
}

Answer 5

Answer №3

While reviewing the question, I noticed a syntax issue in the argument sizes: [number]. Instead of using that format, you could opt for sizes: number[].

You might want to give this a shot:

export function bsColumnClass(sizes: number[]) {
  const sizebs = ['col-xs-', 'col-sm-', 'col-md-', 'col-lg-'];

  sizes = sizes || [12, 12, 12, 12];

  const className = sizes
    .map(function callback(value, index, array) {
      return sizebs[index].concat(value.toString());
    })
    .join(' ');

  return className;
}

//bsColumnClass([1, 2, 6, 3]);

Answer 6

While reviewing the question, I noticed a syntax issue in the argument sizes: [number]. Instead of using that format, you could opt for sizes: number[].

You might want to give this a shot:

export function bsColumnClass(sizes: number[]) {
  const sizebs = ['col-xs-', 'col-sm-', 'col-md-', 'col-lg-'];

  sizes = sizes || [12, 12, 12, 12];

  const className = sizes
    .map(function callback(value, index, array) {
      return sizebs[index].concat(value.toString());
    })
    .join(' ');

  return className;
}

//bsColumnClass([1, 2, 6, 3]);

Answer 7

Answer №4

Recently encountered a similar issue with an Ngx-chart library. Running Angular version 14.2.6

The solution that worked for me was to store the properties in individual variables rather than together.

w = 12;
x = 12;
y = 12;
z = 12;

By doing this, you can directly use these variables in your markup.

[attrName]="[w, x, y, z]"

Answer 8

Recently encountered a similar issue with an Ngx-chart library. Running Angular version 14.2.6

The solution that worked for me was to store the properties in individual variables rather than together.

w = 12;
x = 12;
y = 12;
z = 12;

By doing this, you can directly use these variables in your markup.

[attrName]="[w, x, y, z]"

Issue: The data type '[number] | [number, number, number, number]' cannot be matched with the type '[number]'

Answer №1

Answer №2

Answer №3

Answer №4

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