Encountering an error message in Angular 2/Typescript: "indexOf is not a

Question

Encountering an error message in Angular 2/Typescript: "indexOf is not a

Struggling to understand this...

In my Angular 2 component, I have a function named filterProducts that is executed whenever a user interacts with a checkbox. Currently, the function identifies all checkboxes marked with a specific class name, retrieves their values, and then tries to organize an array. It seems straightforward...

// Executed when any checkbox is selected or deselected

filterProducts() {

// Retrieve all "Program" checkboxes that are selected
var programsToInclude = $(".programCheckbox:checkbox:checked").map(function () { return this.value; });

// If there are any selected "Program" checkboxes, filter the list accordingly
if (programsToInclude)
    this.filteredProducts = this.filteredProducts.filter(x => programsToInclude.indexOf(x.programName) > -1);
}

Why am I encountering this error?

ORIGINAL EXCEPTION: TypeError: programsToInclude.indexOf is not a function

Seems like programsToInclude should be a string array with this function included, right?

javascript angular typescript

Answer 1

Answer №1

programsToInclude is actually a jQuery object, not an array. While jQuery objects have many array methods, they do not have all of them.

If you use jQuery#map, you will need to add a .get() at the end in order to obtain an array:

var programsToInclude = $(".programCheckbox:checkbox:checked").map(function () { return this.value; }).get();
// ---------------------------------------------------------------------------------------------------^^^^
if (programsToInclude) { // <== This check is unnecessary, as explained below
    this.filteredProducts = this.filteredProducts.filter(x => a.indexOf(x.programName) > -1);
}

Alternatively, you can use get earlier to retrieve a native array and adjust your filter call accordingly:

var programsToInclude = $(".programCheckbox:checkbox:checked").get().map(function(e) { return e.value; });
// -----------------------------------------------------------------^^^^----------^-----------^
if (programsToInclude) { // <== Again, see explanation below
    this.filteredProducts = this.filteredProducts.filter(x => programsToInclude.indexOf(x.programName) > -1);
}

In both scenarios, programsToInclude will be transformed into an array. If you plan on converting it back into a jQuery object later on, you will need to convert it again. In such cases, keeping the array separate might be beneficial:

var programsToInclude = $(".programCheckbox:checkbox:checked").map(function(e) { return e.value; });
if (programsToInclude) { // <== Same note applies here
    let a = this.programsToInclude.get();
    this.filteredProducts = this.filteredProducts.filter(x => a.indexOf(x.programName) > -1);
}

Explanation on why the initial check is redundant: A jQuery object, even if empty, will always evaluate to true. To determine if it's empty, you should use if (obj.length). However, conducting a check before using filter is futile, as filter will simply do nothing when operating on an empty object.

Answer 2

programsToInclude is actually a jQuery object, not an array. While jQuery objects have many array methods, they do not have all of them.

If you use jQuery#map, you will need to add a .get() at the end in order to obtain an array:

var programsToInclude = $(".programCheckbox:checkbox:checked").map(function () { return this.value; }).get();
// ---------------------------------------------------------------------------------------------------^^^^
if (programsToInclude) { // <== This check is unnecessary, as explained below
    this.filteredProducts = this.filteredProducts.filter(x => a.indexOf(x.programName) > -1);
}

Alternatively, you can use get earlier to retrieve a native array and adjust your filter call accordingly:

var programsToInclude = $(".programCheckbox:checkbox:checked").get().map(function(e) { return e.value; });
// -----------------------------------------------------------------^^^^----------^-----------^
if (programsToInclude) { // <== Again, see explanation below
    this.filteredProducts = this.filteredProducts.filter(x => programsToInclude.indexOf(x.programName) > -1);
}

In both scenarios, programsToInclude will be transformed into an array. If you plan on converting it back into a jQuery object later on, you will need to convert it again. In such cases, keeping the array separate might be beneficial:

var programsToInclude = $(".programCheckbox:checkbox:checked").map(function(e) { return e.value; });
if (programsToInclude) { // <== Same note applies here
    let a = this.programsToInclude.get();
    this.filteredProducts = this.filteredProducts.filter(x => a.indexOf(x.programName) > -1);
}

Explanation on why the initial check is redundant: A jQuery object, even if empty, will always evaluate to true. To determine if it's empty, you should use if (obj.length). However, conducting a check before using filter is futile, as filter will simply do nothing when operating on an empty object.

Encountering an error message in Angular 2/Typescript: "indexOf is not a

Answer №1

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