TypeScript utility types for deriving API types

<p>I have full TypeScript types for my API responses and need derived types: making all fields optional for updates, picking a subset for list views, omitting sensitive fields, and requiring specific fields.</p>

<p>TypeScript utility type composition:</p> <div class="highlight"><pre><span></span><code><span class="kd">interface</span><span class="w"> </span><span class="nx">Trace</span><span class="w"> </span><span class="p">{</span> <span class="w"> </span><span class="nx">id</span><span class="o">:</span><span class="w"> </span><span class="kt">string</span><span class="p">;</span> <span class="w"> </span><span class="nx">title</span><span class="o">:</span><span class="w"> </span><span class="kt">string</span><span class="p">;</span> <span class="w"> </span><span class="nx">context_text</span><span class="o">:</span><span class="w"> </span><span class="kt">string</span><span class="p">;</span> <span class="w"> </span><span class="nx">solution_text</span><span class="o">:</span><span class="w"> </span><span class="kt">string</span><span class="p">;</span> <span class="w"> </span><span class="nx">trust_score</span><span class="o">:</span><span class="w"> </span><span class="kt">number</span><span class="p">;</span> <span class="w"> </span><span class="nx">is_flagged</span><span class="o">:</span><span class="w"> </span><span class="kt">boolean</span><span class="p">;</span><span class="w"> </span><span class="c1">// internal</span> <span class="w"> </span><span class="nx">contributor_id</span><span class="o">:</span><span class="w"> </span><span class="kt">string</span><span class="p">;</span><span class="w"> </span><span class="c1">// sensitive</span> <span class="w"> </span><span class="nx">created_at</span><span class="o">:</span><span class="w"> </span><span class="kt">string</span><span class="p">;</span> <span class="w"> </span><span class="nx">tags</span><span class="o">:</span><span class="w"> </span><span class="kt">Tag</span><span class="p">[];</span> <span class="p">}</span> <span class="c1">// Derived types:</span> <span class="kr">type</span><span class="w"> </span><span class="nx">TraceListItem</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nx">Pick</span><span class="o">&lt;</span><span class="nx">Trace</span><span class="p">,</span><span class="w"> </span><span class="s1">'id'</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="s1">'title'</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="s1">'trust_score'</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="s1">'created_at'</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="s1">'tags'</span><span class="o">&gt;</span><span class="p">;</span> <span class="kr">type</span><span class="w"> </span><span class="nx">PublicTrace</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nx">Omit</span><span class="o">&lt;</span><span class="nx">Trace</span><span class="p">,</span><span class="w"> </span><span class="s1">'is_flagged'</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="s1">'contributor_id'</span><span class="o">&gt;</span><span class="p">;</span> <span class="kr">type</span><span class="w"> </span><span class="nx">TraceUpdate</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nx">Partial</span><span class="o">&lt;</span><span class="nx">Pick</span><span class="o">&lt;</span><span class="nx">Trace</span><span class="p">,</span><span class="w"> </span><span class="s1">'title'</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="s1">'context_text'</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="s1">'solution_text'</span><span class="o">&gt;&gt;</span><span class="p">;</span> <span class="kr">type</span><span class="w"> </span><span class="nx">TraceCreate</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nx">Required</span><span class="o">&lt;</span><span class="nx">Pick</span><span class="o">&lt;</span><span class="nx">Trace</span><span class="p">,</span><span class="w"> </span><span class="s1">'title'</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="s1">'context_text'</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="s1">'solution_text'</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="o">&amp;</span> <span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="nx">tags?</span><span class="o">:</span><span class="w"> </span><span class="kt">string</span><span class="p">[];</span><span class="w"> </span><span class="nx">agent_model?</span><span class="o">:</span><span class="w"> </span><span class="kt">string</span><span class="p">;</span><span class="w"> </span><span class="p">};</span> <span class="c1">// Extract string literal union from const object:</span> <span class="kd">const</span><span class="w"> </span><span class="nx">STATUS</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="nx">pending</span><span class="o">:</span><span class="w"> </span><span class="s1">'pending'</span><span class="p">,</span><span class="w"> </span><span class="nx">validated</span><span class="o">:</span><span class="w"> </span><span class="s1">'validated'</span><span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="kr">as</span><span class="w"> </span><span class="kd">const</span><span class="p">;</span> <span class="kr">type</span><span class="w"> </span><span class="nx">TraceStatus</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="ow">typeof</span><span class="w"> </span><span class="nx">STATUS</span><span class="p">[</span><span class="nx">keyof</span><span class="w"> </span><span class="ow">typeof</span><span class="w"> </span><span class="nx">STATUS</span><span class="p">];</span><span class="w"> </span><span class="c1">// 'pending' | 'validated'</span> <span class="c1">// Deep partial for nested updates:</span> <span class="kr">type</span><span class="w"> </span><span class="nx">DeepPartial</span><span class="o">&lt;</span><span class="nx">T</span><span class="o">&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="p">[</span><span class="nx">K</span><span class="w"> </span><span class="ow">in</span><span class="w"> </span><span class="nx">keyof</span><span class="w"> </span><span class="nx">T</span><span class="p">]</span><span class="nx">?</span><span class="o">:</span><span class="w"> </span><span class="kt">T</span><span class="p">[</span><span class="nx">K</span><span class="p">]</span><span class="w"> </span><span class="k">extends</span><span class="w"> </span><span class="nx">object</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="nx">DeepPartial</span><span class="o">&lt;</span><span class="nx">T</span><span class="p">[</span><span class="nx">K</span><span class="p">]</span><span class="o">&gt;</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="nx">T</span><span class="p">[</span><span class="nx">K</span><span class="p">]</span><span class="w"> </span><span class="p">};</span> </code></pre></div> <p>Key points: - Pick: keep specified keys. Omit: remove specified keys - Partial: all optional. Required: all required. Readonly: prevent mutation - Combine with &amp; (intersection) to add new fields to derived types - typeof CONST[keyof typeof CONST] extracts union of values from const object</p>