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Source Code for 'Essential TypeScript' by Adam Freeman

License: Other

TypeScript 71.02% JavaScript 10.05% HTML 6.78% Dockerfile 0.77% CSS 1.07% Vue 10.31%

essential-typescript's Introduction

Apress Source Code

This repository accompanies Essential TypeScript by Adam Freeman (Apress, 2019).

Download the files as a zip using the green button, or clone the repository to your machine using Git.

Releases

Release v1.0 corresponds to the code in the published book, without corrections or updates.

Contributions

See the file Contributing.md for more information on how you can contribute to this repository.

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essential-typescript's Issues

Object.setPrototypeOf() not best practice at page 80 and elsewhere too

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/setPrototypeOf

Object.setPrototypeOf() has problems, avoid it, instead use Object.create
Replace:
Object.setPrototypeOf(TaxedProduct.prototype,Product.prototype); with
TaxedProduct.prototype = Object.create(Product.prototype)
Object.defineProperty(TaxedProduct.prototype,"constructor",{enumerable:false,value:TaxedProduct)

p52 Defect in example code

function sumPrices(...numbers){
return numbers.reduce(function(total,value){
return total + (Number.isNaN(Number(val)) ? 0 : Number(val));
}, 0);
}

The book say "To ensure the function produce a useful sum of its parameter values, however they are received......

sumPrices(100,200,true)
return 301 because Number(true) is 1
and there are other edge cases (as Infinity for example)

p100 bug

export function applyDiscount(product, discount = 5) {
    product.price = product.price - 5; // <- should be ** product.price - discount **
}

Error in Table 3-2 (Page 55)

The definition for unshift(item) appears twice.

Error on Page 44

The first six types in the table are the JavaScript primitive data types. The primitive types are always available, and every value in a JavaScript application either is a primitive type itself or is composed from primitive types. The sixth type is object and is used to represent objects.

Should be the seventh type

Spread Operator of add function in Chapter 13

I found maybe there is a typo of add function in chapter 13.

add(...newItems: T[]): void {
        this.items.push(...newItems);
}

should be ???

add(newItems: T[]): void {
        this.items.push(...newItems);
}

With the spread syntax in the argument, It will be

col.add([{ name: 'prod1', price: 10 }, {name: 'prod2', price: 20}])
col.add([{ name: 'prod3', price: 30 }, {name: 'prod4', price: 40}])
// the result of items
[
    [{
        { name: 'prod1', price: 10 }, 
        {name: 'prod2', price: 20}
    }],
    [{
        { name: 'prod3', price: 30 }, 
        {name: 'prod4', price: 40}
    }]
]

Is it designated?

p53 Initial value parameter to `reduce` function silently dropped

function sumPrices (...numbers {
  return numbers.reduce(function(total, val) {
    return total + (Number.isNaN(Number(val))? 0 : Number(val))
  }**, 0**)

function sumPrices (...numbers {
  return numbers.reduce((total, val) => 
    total + (Number.isNaN(Number(val))? 0 : Number(val)) /* **, 0** */)

Choose to "Hide complete items"
Choose "Complete items"
Hit return
All previously completed items are now marked as incomplete

One possible solution:

function promptComplete() : void {

  ...

        collection.getTodoItems(true).forEach(item =>
            (!showCompleted && item.complete) ||
                collection.markComplete(item.id, completedTasks.find(id => id === item.id) != undefined))

  ...

}