Encountered "Function undefined error when invoking within a map in TypeScript"

Question

Encountered "Function undefined error when invoking within a map in TypeScript"

In my function, there is a map that looks like this:

mainFunc(){
// other logics

    data.map(function (item) {
      item.number = Math.round(item.number);
      item.total = item.last - item.first;
      item.quantity= item?.quantity ? quantityRange(item?.quantity): '';
    }); 

// other logics
}


quantityRange(quantity){
if(quantity){
   if(quantity < 100) return "Less Quantity";
   if(quantity < 500) return "Average Quantity";
   else return "Good Quantity"
   }
}

I placed the quantityRange() outside the mainFunc() and then called it within the ternary operator inside the map. However, upon running the code, I encountered an error: quantityRange() is not defined. Does this mean we cannot use functions in this way inside the map function in TypeScript?

I would greatly appreciate any assistance with this issue.

javascript typescript

Answer 1

Answer №1

executeMainFunction(){
// additional operations
    const current = this; // ensure the context remains intact
    data.map(function (element) {
      element.number = Math.round(element.number);
      element.total = element.last - element.first;
      element.quantity= element?.quantity ? current.calculateQuantityRange(element?.quantity): '';
    }); 

// additional operations
}

When using the method with 'this' keyword, remember to bind it properly. There are various approaches to binding, such as storing it in a variable.

Answer 2

executeMainFunction(){
// additional operations
    const current = this; // ensure the context remains intact
    data.map(function (element) {
      element.number = Math.round(element.number);
      element.total = element.last - element.first;
      element.quantity= element?.quantity ? current.calculateQuantityRange(element?.quantity): '';
    }); 

// additional operations
}

When using the method with 'this' keyword, remember to bind it properly. There are various approaches to binding, such as storing it in a variable.

Answer 3

Answer №2

The reason for the error is because you forgot to define it properly. You must use the keyword function to create both of your functions. Additionally, there should not be a space between data.map(function (item); the parentheses must stick together. There were other syntax mistakes as well, but most of them have been corrected in the revised code.
The correct format should look like this:

function mainFunc() {
// additional logic

    data.map(function(item) {
        item.number = Math.round(item.number);
        item.total = item.last - item.first;
        item.quantity = item?.quantity ? quantityRange(item?.quantity): ''; // Issue lies with this line.
    }); 

// additional logic
};


function quantityRange(quantity) {
    if (quantity) {
        if (quantity < 100) {
            return "Less Quantity";
        }
        else if (quantity < 500) {
            return "Average Quantity";
        }
        else {
            return "Good Quantity";
        };
    };
};

I couldn't quite understand the purpose of line 6, but that seems to be where the mistake occurred. Could you clarify what you are trying to accomplish with that line so I can assist in correcting its syntax?

Answer 4

The reason for the error is because you forgot to define it properly. You must use the keyword function to create both of your functions. Additionally, there should not be a space between data.map(function (item); the parentheses must stick together. There were other syntax mistakes as well, but most of them have been corrected in the revised code.
The correct format should look like this:

function mainFunc() {
// additional logic

    data.map(function(item) {
        item.number = Math.round(item.number);
        item.total = item.last - item.first;
        item.quantity = item?.quantity ? quantityRange(item?.quantity): ''; // Issue lies with this line.
    }); 

// additional logic
};


function quantityRange(quantity) {
    if (quantity) {
        if (quantity < 100) {
            return "Less Quantity";
        }
        else if (quantity < 500) {
            return "Average Quantity";
        }
        else {
            return "Good Quantity";
        };
    };
};

I couldn't quite understand the purpose of line 6, but that seems to be where the mistake occurred. Could you clarify what you are trying to accomplish with that line so I can assist in correcting its syntax?

Encountered "Function undefined error when invoking within a map in TypeScript"

Answer №1

Answer №2

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