JavaScript encountered an Uncaught TypeError when trying to read the property 'length' of an undefined value within an array

Question

JavaScript encountered an Uncaught TypeError when trying to read the property 'length' of an undefined value within an array

Currently, I am encountering an issue with passing arguments into a function. When I pass two arguments into the specified array setup and try to log them using console.log, an exception is thrown. Strangely, if I remove the arguments from the parameters, the function runs smoothly. Can anyone shed light on why this might be happening and provide guidance on how to resolve it?

var musicians = ["Paul", "John", "Yuri"];

var instruments = ["Drums", "Guitar", "Chelo"];

function theBeatlesPlay(musicians, instruments) {

    var empty = [];

    for (var i = 0; i < **musicians.length**; i++) {

      var str = musicians[i] + " plays " + instruments[i];
      empty = str;
      **console.log(empty)**;
    }
    }

    theBeatlesPlay();

javascript arrays

Answer 1

Answer №1

Ensure to provide the arguments when calling the function.

playMusicianInstruments(musicians, instruments);

var musicians = ["Liam", "Noel", "David"],
    instruments = ["Vocals", "Guitar", "Bass"];

function playMusicianInstruments(musicians, instruments) {
  var duo = [];
  for (var j = 0; j < musicians.length; j++) {
    var message = musicians[j] + " performs with " + instruments[j];
    duo = message;
    console.log(duo);
  }
}

playMusicianInstruments(musicians, instruments);

Answer 2

Ensure to provide the arguments when calling the function.

playMusicianInstruments(musicians, instruments);

var musicians = ["Liam", "Noel", "David"],
    instruments = ["Vocals", "Guitar", "Bass"];

function playMusicianInstruments(musicians, instruments) {
  var duo = [];
  for (var j = 0; j < musicians.length; j++) {
    var message = musicians[j] + " performs with " + instruments[j];
    duo = message;
    console.log(duo);
  }
}

playMusicianInstruments(musicians, instruments);

Answer 3

Answer №2

Explained: Whenever you define a function with parameters, those parameters are considered as local variables. This means that even if you have existing variables named musicians and instruments, the function's parameters with the same names will take precedence within the function scope.

To resolve this dilemma, there are two approaches:

Omit the parameters in the function declaration (if your goal is to access external variables without using them as parameters):

var musicians = ["Paul", "John", "Yuri"],
    instruments = ["Drums", "Guitar", "Chelo"];


/* Precondition: musicians and instruments arrays defined externally */
function theBeatlesPlay(/* No params */) {

    var empty = [];

    for (var i = 0; i < musicians.length; i++) {

        var str = musicians[i] + " plays " + instruments[i];
        empty = str;
        console.log(empty);
    }
}

Call the function while passing the previously declared arrays as arguments:

/* 
    musicians and instruments variables act as LOCAL variables within the function 
*/
function theBeatlesPlay(musicians, instruments) {

    var empty = [];

    for (var i = 0; i < musicians.length; i++) {

        var str = musicians[i] + " plays " + instruments[i];
        empty = str;
        console.log(empty);
    }
}

theBeatlesPlay(musicians, instruments);

I'd recommend avoiding variable names like empty unless it remains empty by design. Otherwise, consider making it a constant.

Additionally, analyzing the type of exception thrown and its corresponding message can be beneficial for troubleshooting.

Answer 4

Explained: Whenever you define a function with parameters, those parameters are considered as local variables. This means that even if you have existing variables named musicians and instruments, the function's parameters with the same names will take precedence within the function scope.

To resolve this dilemma, there are two approaches:

Omit the parameters in the function declaration (if your goal is to access external variables without using them as parameters):

var musicians = ["Paul", "John", "Yuri"],
    instruments = ["Drums", "Guitar", "Chelo"];


/* Precondition: musicians and instruments arrays defined externally */
function theBeatlesPlay(/* No params */) {

    var empty = [];

    for (var i = 0; i < musicians.length; i++) {

        var str = musicians[i] + " plays " + instruments[i];
        empty = str;
        console.log(empty);
    }
}

Call the function while passing the previously declared arrays as arguments:

/* 
    musicians and instruments variables act as LOCAL variables within the function 
*/
function theBeatlesPlay(musicians, instruments) {

    var empty = [];

    for (var i = 0; i < musicians.length; i++) {

        var str = musicians[i] + " plays " + instruments[i];
        empty = str;
        console.log(empty);
    }
}

theBeatlesPlay(musicians, instruments);

I'd recommend avoiding variable names like empty unless it remains empty by design. Otherwise, consider making it a constant.

Additionally, analyzing the type of exception thrown and its corresponding message can be beneficial for troubleshooting.

Answer 5

Answer №3

Make sure you are passing the necessary arguments to your function in order for it to work correctly. It is important to call the function properly by providing the required data before executing it. When dealing with multiple functions, keep track of the flow of information to avoid confusion and potential errors.

var musicians = ["Paul", "John", "Yuri"];

var instruments = ["Drums", "Guitar", "Chelo"];

var errlog = theBeatlesPlay(musicians, instruments);

console.log(errlog);

function theBeatlesPlay(musicians_val, instruments_val) {

var empty = [];

for (var i = 0; i < musicians_val.length; i++) {

var str = musicians_val[i] + " plays " + instruments_val[i];
      empty = str;
     
    }
    return empty;
 }

Answer 6

Make sure you are passing the necessary arguments to your function in order for it to work correctly. It is important to call the function properly by providing the required data before executing it. When dealing with multiple functions, keep track of the flow of information to avoid confusion and potential errors.

var musicians = ["Paul", "John", "Yuri"];

var instruments = ["Drums", "Guitar", "Chelo"];

var errlog = theBeatlesPlay(musicians, instruments);

console.log(errlog);

function theBeatlesPlay(musicians_val, instruments_val) {

var empty = [];

for (var i = 0; i < musicians_val.length; i++) {

var str = musicians_val[i] + " plays " + instruments_val[i];
      empty = str;
     
    }
    return empty;
 }

JavaScript encountered an Uncaught TypeError when trying to read the property 'length' of an undefined value within an array

Answer №1

Answer №2

Answer №3

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