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数値の文字列をパースしよう
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Matsui Masashi
June 28, 2024
Programming
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数値の文字列をパースしよう
Matsui Masashi
June 28, 2024
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Transcript
ͷจࣈྻΛύʔε͠Α͏ Niigata 5min Tech #9 @circled9 1
ࣗݾհ @circled9 দҪɹਖ਼ࢤ / Matsui Masashi גࣜձࣾϞχΫϧ TypeScriptͰ৭ʑܭࢉ͢ΔࣄΛ ͯ͠·͢ 2
ͷจࣈྻͷύʔε • JavaScriptͰͷจࣈྻͷύʔε͠·͢ΑͶʁ • parseInt, parseFloat, NumberͷͲΕ͍͍͔͑Έ·ͤΜ ͔ʁ • ͱ͍͏Θ͚Ͱ৭ʑύʔεͯ͠Έ·ͨ͠
3
4
"123" 5
ී௨ͷͷ߹ > parseInt("123") <- 123 > parseFloat("123") <- 123 >
Number("123") <- 123 6
"123,456" 7
ܻ̏۠Γͷͷ߹ > parseInt("123,456") <- 123 > parseFloat("123,456") <- 123 >
Number("123,456") <- NaN 8
"123_456" 9
Numeric Separator • ES2021ͷه๏ • ͷ۠Γจࣈͱͯ͠ΞϯμʔείΞ͕͑Δ > 123_456_789 <- 123456789
10
ΞϯμʔείΞ۠Γͷͷ߹ > parseInt("123_456") <- 123 > parseFloat("123_456") <- 123 >
Number("123_456") <- NaN 11
ͷ·ͱΊ • parseIntͱparseFloatҎ֎ͷจࣈ͕ग़ͯ͘Δ·Ͱύʔε͢ Δ • Numberมͳจࣈ͕͋ΔͱNaNΛฦ͢ 12
খ 13
"1.23" 14
ී௨ͷখͷ߹ > parseInt("1.23") <- 1 > parseFloat("1.23") <- 1.23 >
Number("1.23") <- 1.23 15
".123" 16
খͷলུܗͷ߹ > parseInt(".123") <- NaN > parseFloat(".123") <- 0.123 >
Number(".123") <- 0.123 17
"192.168.1.1" 18
খͰͳ͍Կ͔ͩͬͨ߹ > parseInt("192.168.1.1") <- 192 > parseFloat("192.168.1.1") <- 192.168 >
Number("192.168.1.1") <- NaN 19
খͷ·ͱΊ • parseIntҎ֎ͷจࣈ͕ग़ͯ͘Δ·Ͱύʔε͢Δ • parseFloatখͱͯ͠ύʔεͰ͖Δͱ͜Ζ·Ͱύʔε͢Δ • Numberখͱ͓͔͍ͯ͠͠߹NaNΛฦ͢ 20
ͦͷଞͷ 21
"1.234E-5" 22
ࢦදهͷ߹ > parseInt("1.234E-5") <- 1 > parseFloat("1.234E-5") <- 0.00001234 >
Number("1.234E-5") <- 0.00001234 23
"Infinity" 24
In fi nityͷ߹ > parseInt("-Infinity") <- NaN > parseFloat("-Infinity") <-
-Infinity > Number("-Infinity") <- -Infinity 25
" 123 " 26
લޙʹۭന͕͋Δ߹ > parseInt(" 123 ") <- 123 > parseFloat(" 123
") <- 123 > Number(" 123 ") <- 123 27
" 1 2 3 " 28
్தʹۭന͕͋Δ߹ > parseInt(" 1 2 3 ") <- 1 >
parseFloat(" 1 2 3 ") <- 1 > Number(" 1 2 3 ") <- NaN 29
ͦͷଞͷͷ·ͱΊ • parseFloatNumberࢦදهInfinityʹରԠ͍ͯ͠Δ • Ͳͷؔจࣈྻͷલޙͷۭനແࢹ͢Δ • Ͳͷؔจࣈྻͷ్தͷۭനύʔεͰ͖ͳ͍จࣈѻ͍ʹͳΔ 30
ۭͷ 31
"" 32
ۭจࣈͷ߹ > parseInt("") <- NaN > parseFloat("") <- NaN >
Number("") <- 0 33
null 34
nullͷ߹ > parseInt(null) <- NaN > parseFloat(null) <- NaN >
Number(null) <- 0 35
undefined 36
unde fi nedͷ߹ > parseInt(undefined) <- NaN > parseFloat(undefined) <-
NaN > Number(undefined) <- NaN 37
ۭͷͷ·ͱΊ • NumberۭനจࣈͱnullΛύʔε͢Δͱ0Λฦ͢ • ҰํɺparseIntͱparseFloatNaNΛฦ͢ • ͲͷؔundefinedΛύʔε͢ΔͱNaNΛฦ͢ 38
·ͱΊ 39
·ͱΊ • parseIntࣈͷ෦ΛͰ͖Δ͚ͩύʔε͢Δ • parseFloatখͬΆ͍෦ΛͰ͖Δ͚ͩύʔε͢Δ • Numberมͳจࣈ͕ೖͬͯΔͱNaNΛฦ͢ • Numberͷۭനจࣈͱnullͷڍಈʹҙ 40
͓·͚ 41
͜ΕΒҰॹ > parseInt === Number.parseInt <- true > parseFloat ===
Number.parseFloat <- true 42
͜ΕҰॹ > +"" === Number("") <- true 43