c9a03dc659
• A type guard of the form expr1 || expr2 o when true, narrows the type of x to T1 | T2, where T1 is the type of x narrowed by expr1 when true, and T2 is the type of x narrowed by expr1 when false and then by expr2 when true, or o when false, narrows the type of x by expr1 when false and then by expr2 when false.
46 lines
No EOL
1.8 KiB
TypeScript
46 lines
No EOL
1.8 KiB
TypeScript
var str: string;
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var bool: boolean;
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var num: number;
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var strOrNum: string | number;
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var strOrNumOrBool: string | number | boolean;
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var numOrBool: number | boolean;
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class C { private p; }
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var c: C;
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var cOrBool: C| boolean;
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var strOrNumOrBoolOrC: string | number | boolean | C;
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// A type guard of the form expr1 || expr2
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// - when true, narrows the type of x to T1 | T2, where T1 is the type of x narrowed by expr1 when true,
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// and T2 is the type of x narrowed by expr1 when false and then by expr2 when true, or
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// - when false, narrows the type of x by expr1 when false and then by expr2 when false.
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// (typeguard1 || typeguard2)
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if (typeof strOrNumOrBool === "string" || typeof strOrNumOrBool === "number") {
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strOrNum = strOrNumOrBool; // string | number
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}
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else {
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bool = strOrNumOrBool; // boolean
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}
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// (typeguard1 || typeguard2 || typeguard3)
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if (typeof strOrNumOrBoolOrC === "string" || typeof strOrNumOrBoolOrC === "number" || typeof strOrNumOrBoolOrC === "boolean") {
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strOrNumOrBool = strOrNumOrBoolOrC; // string | number | boolean
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}
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else {
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c = strOrNumOrBoolOrC; // C
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}
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// (typeguard1 || typeguard2 || typeguard11(onAnotherType))
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if (typeof strOrNumOrBoolOrC === "string" || typeof strOrNumOrBoolOrC === "number" || typeof strOrNumOrBool !== "boolean") {
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var r1: string | number | boolean | C = strOrNumOrBoolOrC; // string | number | boolean | C
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var r2: string | number | boolean = strOrNumOrBool;
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}
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else {
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cOrBool = strOrNumOrBoolOrC; // C | boolean
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bool = strOrNumOrBool; // boolean
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}
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// (typeguard1) || simpleExpr
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if (typeof strOrNumOrBool === "string" || numOrBool !== strOrNumOrBool) {
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var r3: string | number | boolean = strOrNumOrBool; // string | number | boolean
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}
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else {
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numOrBool = strOrNumOrBool; // number | boolean
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} |