{"id":1155,"date":"2024-02-19T10:56:40","date_gmt":"2024-02-19T09:56:40","guid":{"rendered":"https:\/\/greladesign.co\/blog\/?p=1155"},"modified":"2024-02-19T10:56:40","modified_gmt":"2024-02-19T09:56:40","slug":"typescript-make-stricter-required","status":"publish","type":"post","link":"https:\/\/greladesign.co\/blog\/2024\/02\/19\/typescript-make-stricter-required\/","title":{"rendered":"TypeScript: Make stricter Required"},"content":{"rendered":"\n<p>When you have a type with optional props, then to make those props required you can use <code>Required<\/code> like so:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-1\" data-shcb-language-name=\"TypeScript\" data-shcb-language-slug=\"typescript\"><span><code class=\"hljs language-typescript\"><span class=\"hljs-keyword\">type<\/span> TTypeWithOptional = { \n  a?: <span class=\"hljs-built_in\">string<\/span>;\n  b: <span class=\"hljs-built_in\">string<\/span> | <span class=\"hljs-literal\">undefined<\/span>;\n  c?: <span class=\"hljs-built_in\">string<\/span> | <span class=\"hljs-literal\">null<\/span> \n};\n\n<span class=\"hljs-keyword\">type<\/span> TRequired = Required&lt;TTypeWithOptional&gt;;\n<span class=\"hljs-comment\">\/*\n\/\/ result\ntype TRequired = {\n    a: string;\n    b: string | undefined;\n    c: string | null;\n}\n*\/<\/span><\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-1\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">TypeScript<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">typescript<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<!--more-->\n\n\n\n<p>As you can see it did removed the optionality <code>?:<\/code> but you may still, counterintuitively, encounter an &#8220;optional&#8221; prop, e.g. <code>b<\/code> being <code>undefined<\/code>. To solve this requirement you may want to use this strict required type:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-2\" data-shcb-language-name=\"TypeScript\" data-shcb-language-slug=\"typescript\"><span><code class=\"hljs language-typescript\"><span class=\"hljs-keyword\">export<\/span> <span class=\"hljs-keyword\">type<\/span> TStrictRequired&lt;T, E = <span class=\"hljs-literal\">null<\/span> | <span class=\"hljs-literal\">undefined<\/span>&gt; = { \n  &#91;P <span class=\"hljs-keyword\">in<\/span> keyof T]-?: Exclude&lt;T&#91;P], E&gt; \n};<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-2\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">TypeScript<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">typescript<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Which does the same the <code>Required<\/code> does but also filters out &#8220;optional&#8221; values by excluding <code>undefined | null<\/code> (that was my requirement). <\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-3\" data-shcb-language-name=\"TypeScript\" data-shcb-language-slug=\"typescript\"><span><code class=\"hljs language-typescript\"><span class=\"hljs-keyword\">type<\/span> TStrict = TStrictRequired&lt;TTypeWithOptional&gt;;\n<span class=\"hljs-comment\">\/*\n\/\/ result\ntype TStrict = {\n    a: string;\n    b: string;\n    c: string;\n}\n*\/<\/span><\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-3\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">TypeScript<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">typescript<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>If you need <code>null<\/code> you can modify default behaviour, by using second generic parameter <code>E<\/code> and change it to exclude <code>undefined<\/code> only:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-4\" data-shcb-language-name=\"JavaScript\" data-shcb-language-slug=\"javascript\"><span><code class=\"hljs language-javascript\">type TStrict = TStrictRequired&lt;TTypeWithOptional, <span class=\"hljs-literal\">undefined<\/span>&gt;;\n<span class=\"hljs-comment\">\/*\n\/\/ result\ntype TStrict = {\n    a: string;\n    b: string;\n    c: string | null;\n}\n*\/<\/span><\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-4\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">JavaScript<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">javascript<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>When you have a type with optional props, then to make those props required you can use Required like so:<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_import_markdown_pro_load_document_selector":0,"_import_markdown_pro_submit_text_textarea":""},"categories":[356],"tags":[368,367,357],"_links":{"self":[{"href":"https:\/\/greladesign.co\/blog\/wp-json\/wp\/v2\/posts\/1155"}],"collection":[{"href":"https:\/\/greladesign.co\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/greladesign.co\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/greladesign.co\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/greladesign.co\/blog\/wp-json\/wp\/v2\/comments?post=1155"}],"version-history":[{"count":2,"href":"https:\/\/greladesign.co\/blog\/wp-json\/wp\/v2\/posts\/1155\/revisions"}],"predecessor-version":[{"id":1157,"href":"https:\/\/greladesign.co\/blog\/wp-json\/wp\/v2\/posts\/1155\/revisions\/1157"}],"wp:attachment":[{"href":"https:\/\/greladesign.co\/blog\/wp-json\/wp\/v2\/media?parent=1155"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/greladesign.co\/blog\/wp-json\/wp\/v2\/categories?post=1155"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/greladesign.co\/blog\/wp-json\/wp\/v2\/tags?post=1155"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}