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Advanced
built-in types
you may not know
Masashi Hirano @shisama
kansai.ts #1
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ฏ ণ࢜ / Masashi Hirano
@shisama_
@shisama
Node.js Core Collaborator
ؔNodeֶԂOrganizer
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TypeScriptʹbuilt-in͞Ε͍ͯΔศརͳܕʹ
͍ͭͯհ͠·͢ʂ
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https://www.typescriptlang.org/docs/handbook/advanced-types.html
ެࣜͷAdvanced TypesಡΜͩ͜ͱ͋Δ?
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Advanced Types
• Conditional TypesMapped TypesͳͲෳࡶͳܕUnion Types
ͳͲศརͳه๏ͳͲΛհ͍ͯ͠Δެࣜͷϖʔδ
• ࠓճͦͷத͔Βbuilt-in͞Ε͍ͯΔศརͳܕΛհ͠·͢
※ܕఆٛΛಡΉʹConditional TypesMapped Types͕ಡ
ΊΔඞཁ͕͋Γ·͢ɻ
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https://github.com/microsoft/TypeScript/blob/master/src/lib/es5.d.ts
5ZQF4DSJQUͷ(JU)VCϦϙδτϦͷ
TSDMJCFTEUTʹఆ͕ٛ͋Δ
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type Partial = {
[P in keyof T]?: T[P];
};
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type Partial = {
[P in keyof T]?: T[P];
};
LFZPG5 ΦϒδΣΫτ
ͷϓϩύςΟ໊Λऔ͍ͬͯΔ
ϓϩύςΟʹ Λ༩ͯ͠PQUJPOBMʹ͍ͯ͠Δ
JO5ͷϓϩύςΟ໊Λ1ʹ֨ೲ͍ͯ͠Δɻ
5<1>ࢦఆͨ͠ϓϩύςΟͷܕ
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Partial
ͯ͢ͷϓϩύςΟΛ0QUJPOBMʹ͢Δ
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Partial
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Partial
6TFSJE͕ඞਢͳͷͰۭΦϒδΣΫτίϯ
ύΠϧΤϥʔʹͳΔɻ
1BSUJBM6TFSͯ͢ͷϓϩύςΟ͕0QUJPOBMʹͳΔͨ
ΊۭΦϒδΣΫτΛೖͰ͖Δ
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type Required = {
[P in keyof T]-?: T[P];
};
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type Required = {
[P in keyof T]-?: T[P];
};
PQUJPOBMͷϓϩύςΟΛOPOPQUJPOBMʹ͢Δ
1BSUJBMͷٯͰ ΛऔΓআ͍͍ͯΔ
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Required
ͯ͢ͷϓϩύςΟΛOPOPQUJPOBMʹ͢Δ
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Required
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Required
ͯ͢ͷϓϩύςΟ͕OPOPQUJPOBMͳͷͰ
JEলུͰ͖ͳ͍
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type Readonly = {
readonly [P in keyof T]: T[P];
};
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type Readonly = {
readonly [P in keyof T]: T[P];
};
ϓϩύςΟͷલʹSFBEPOMZΛॻ͘ͱͦͷϓϩύςΟಡ
ΈऔΓઐ༻ʹͳΔ
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Readonly
ͯ͢ͷϓϩύςΟΛSFBEPOMZʹ͢Δ
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Readonly
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Readonly
ͯ͢ͷϓϩύςΟΛSFBEPOMZͷͨΊ
ೖෆՄೳ
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type Pick = {
[P in K]: T[P];
};
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type Pick = {
[P in K]: T[P];
};
,ʹࢦఆͰ͖Δͷ5ͷϓϩύςΟ໊ͷΈɻ5ʹແ͍ϓϩ
ύςΟ໊Λࢦఆ͢ΔͱΤϥʔʹͳΔ
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Pick
ࢦఆͨ͠ϓϩύςΟͷΈ͢
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Pick
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Pick
ࢦఆͨ͠ϓϩύςΟҎ֎ΤϥʔʹͳΔ
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type Record = {
[P in K]: T;
};
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type Record = {
[P in K]: T;
};
lLFZPGBOZzlTUSJOHcOVNCFScTZNCPMz
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Record
LFZ໊ͱWBMVFͷܕΛࢦఆͨ͠ΦϒδΣΫτܕ
Λ࡞Δ
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Record
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Record
-BTUTBUPcUBOBLBͨΊɺ
TV[VLJΤϥʔʹͳΔ
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Record
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Record
-BTUTBUPcTV[VLJcUBOBLBͨΊɺ
UBOBLB͕ແ͍ͱΤϥʔʹͳΔ
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type Exclude = T extends U ? never : T;
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type Exclude = T extends U ? never : T;
ࡾ߲ԋࢉࢠͷΑ͏ʹ݅ʹΑͬͯܕ͕ܾ·Δ
5͕6Λܧঝ͍ͯ͠Δ߹OFWFSɺͦ͏Ͱͳ͍߹5
OFWFSΛฦ͞ͳ͍ܕɻ
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Exclude
ྻڍ͔Βࢦఆͨ͠ΛऔΓআ͘
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Exclude
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Exclude
औΓআ͍ͨΛೖ͢ΔͱΤϥʔ
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type Extract = T extends U ? T : never;
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type Extract = T extends U ? T : never;
5͕6Λܧঝ͍ͯ͠Δ߹5ɺ
ͦ͏Ͱͳ͍߹OFWFSΛฦ͍ͯ͠Δɻ
ฦ͕͢&YDMVEFͷٯʹͳ͍ͬͯΔ
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Extract
ྻڍͷத͔Βࢦఆͨ͠Λநग़
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Extract
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Extract
நग़ͨ͠Ҏ֎Λೖ͢ΔͱΤϥʔ
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type NonNullable
= T extends null | undefined ? never : T;
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type NonNullable
= T extends null | undefined ? never : T;
OVMM·ͨVOEFpOFEΛܧঝ͍ͯ͠ΔܕͰ͋
ΕOFWFSɺͦ͏Ͱͳ͍߹5Λฦ͍ͯ͠Δ
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NonNullable
OVMMͱVOEFpOFEΛऔΓআ͘
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NonNullable
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NonNullable
OVMMVOEFpOFEೖͰ͖ͳ͍
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type Parameters any>
= T extends (...args: infer P) => any ? P : never;
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type Parameters any>
= T extends (...args: infer P) => any ? P : never;
JOGFSܕਪͨ݁͠ՌΛऔΔ͜ͱ͕Ͱ͖Δ
͜ͷ߹ؔͷҾͷܕΛਪ͍ͯ͠Δɻ
5͕ؔܕ ʜBSHTJOGFS1
BOZͷܧঝͩͬͨ߹ɺ
ਪͨ͠ҾͷܕΛฦ͍ͯ͠Δ
5ؔܕͷΈࢦఆͰ͖Δ
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Parameters
ؔͷҾͷܕΛλϓϧͰऔΔ
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Parameters
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Parameters
ؔͷҾͷܕʹ߹Θͳ͍ͱΤϥʔ
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·ͱΊ
• ศརͳܕ͕TypeScriptຊମʹΈࠐ·Ε͍ͯΔ
• Conditional TypesͱMapped TypesΛͬͯఆٛ͞Ε͍ͯΔ
• ࠓհ͖͠Εͳ͔ͬͨܕͷఆٛsrc/lib/es5.d.tsʹ͋ΔͷͰڵ
ຯ͕͋ΕݟͯΈ͍ͯͩ͘͞
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Thanks.
@shisama_
@shisama