The argument labeled as 'RegExp' cannot be allocated to a parameter labeled as 'string'

Question

The argument labeled as 'RegExp' cannot be allocated to a parameter labeled as 'string'

My current task involves importing an Excel File in the following manner:

onFileChange(event: any) 
  {
    const inputFile: DataTransfer = <DataTransfer>(event.target); 
    const fileReader: FileReader = new FileReader();
    fileReader.onload = (event: any) => 
    {
      const binaryString: string = event.target.result;
      const workBook: XLSX.WorkBook = XLSX.read(binaryString, { type: 'binary', sheetStubs: true}); 
      /* sheetstubs true supposedly shows empty cells but isn't */
      console.log(typeof binaryString)

      const workSheetName: string = workBook.SheetNames[0];
      console.log(workSheetName)
      const workSheet: XLSX.WorkSheet = workBook.Sheets[workSheetName];

      this.data = <Array>(XLSX.utils.sheet_to_json(workSheet, 
      {header: 1, blankrows: true }));


    };
    fileReader.readAsBinaryString(inputFile.files[0]);

  }

My goal is to identify the index (essentially the column number) of any cell that contains the word 'cap' using regex.

I attempted to use regex as shown below to search for the term cap in any cell but encountered the following error,

Argument of type 'RegExp' is not assignable to parameter of type 'string'.

I am puzzled by the meaning of this error message and unsure how to proceed.

getManufacturerDescriptionColumn()
  {
    for (const row in this.data)
    {
      var descIndex = row.indexOf(/cap*/i)
      return descIndex
    }
  }

javascript angular typescript

Answer 1

Answer №1

The String.indexOf() method requires a string as its first argument.

The syntax /<pattern>/ represents a regular expression literal and creates a RegExp object, not a string, as indicated by the error message.

To resolve this issue, use a string instead of a regular expression when calling String.indexOf():

row.indexOf('cap')

Note that this search is case-sensitive. If you need a case-insensitive search, using a regular expression would be more suitable.

In that case, you should utilize the String.search() method. This method expects a RegExp as its first parameter and returns the index of the first match within the string.

A few additional points to consider:

Your current loop will return the result of the first iteration even if no match is found.
The provided regular expression (/cap*/i) searches for 'ca' followed by zero or more 'p' characters. This means it will match 'ca', 'cap', 'capppp', etc.

You may want to modify your code like so:

getManufacturerDescriptionColumn() {
  for (const row in this.data) {
    let matchIndex = row.search(/cap/i);
    if (matchIndex > -1) {
      return matchIndex;
    }
  }
}

Answer 2

The String.indexOf() method requires a string as its first argument.

The syntax /<pattern>/ represents a regular expression literal and creates a RegExp object, not a string, as indicated by the error message.

To resolve this issue, use a string instead of a regular expression when calling String.indexOf():

row.indexOf('cap')

Note that this search is case-sensitive. If you need a case-insensitive search, using a regular expression would be more suitable.

In that case, you should utilize the String.search() method. This method expects a RegExp as its first parameter and returns the index of the first match within the string.

A few additional points to consider:

Your current loop will return the result of the first iteration even if no match is found.
The provided regular expression (/cap*/i) searches for 'ca' followed by zero or more 'p' characters. This means it will match 'ca', 'cap', 'capppp', etc.

You may want to modify your code like so:

getManufacturerDescriptionColumn() {
  for (const row in this.data) {
    let matchIndex = row.search(/cap/i);
    if (matchIndex > -1) {
      return matchIndex;
    }
  }
}

The argument labeled as 'RegExp' cannot be allocated to a parameter labeled as 'string'

Answer №1

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