Addition of ignore notation
Some snippets are designed to show syntax errors or refer to earlier variables. In this case the automated checker needs to avoid compiling them
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@@ -45,7 +45,7 @@ TypeScript can figure the return type out by looking at the return statements, s
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In TypeScript, the number of arguments given to a function has to match the number of parameters the function expects.
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```ts
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```ts-ignore
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function buildName(firstName: string, lastName: string) {
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return firstName + " " + lastName;
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}
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@@ -60,7 +60,7 @@ When they do, their value is `undefined`.
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We can get this functionality in TypeScript by adding a `?` to the end of parameters we want to be optional.
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For example, let's say we want the last name parameter from above to be optional:
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```ts
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```ts-ignore
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function buildName(firstName: string, lastName?: string) {
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if (lastName)
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return firstName + " " + lastName;
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@@ -80,7 +80,7 @@ In TypeScript, we can also set a value that a parameter will be assigned if the
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These are called default-initialized parameters.
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Let's take the previous example and default the last name to `"Smith"`.
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```ts
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```ts-ignore
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function buildName(firstName: string, lastName = "Smith") {
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return firstName + " " + lastName;
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}
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@@ -115,7 +115,7 @@ Unlike plain optional parameters, default-initialized parameters don't *need* to
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If a default-initialized parameter comes before a required parameter, users need to explicitly pass `undefined` to get the default initialized value.
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For example, we could write our last example with only a default initializer on `firstName`:
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```ts
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```ts-ignore
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function buildName(firstName = "Will", lastName: string) {
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return firstName + " " + lastName;
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}
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@@ -134,7 +134,7 @@ In JavaScript, you can work with the arguments directly using the `arguments` va
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In TypeScript, you can gather these arguments together into a variable:
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```ts
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```ts-ignore
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function buildName(firstName: string, ...restOfName: string[]) {
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return firstName + " " + restOfName.join(" ");
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}
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@@ -148,7 +148,7 @@ The compiler will build an array of the arguments passed in with the name given
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The ellipsis is also used in the type of the function with rest parameters:
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```ts
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```ts-ignore
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function buildName(firstName: string, ...restOfName: string[]) {
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return firstName + " " + restOfName.join(" ");
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}
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