我有一个存储false或true的变量，但我需要分别为0或1。我该怎么做呢?
当前回答
我已经测试了所有这些例子，我做了一个基准测试，最后我建议你选择较短的一个，它不会影响性能。
运行在Ubuntu服务器14.04,nodejs v8.12.0 - 26/10/18
let i = 0;
console.time("TRUE test1")
i=0;
for(;i<100000000;i=i+1){
true ? 1 : 0;
}
console.timeEnd("TRUE test1")
console.time("FALSE test2")
i=0;
for(;i<100000000;i=i+1){
false ? 1 : 0;
}
console.timeEnd("FALSE test2")
console.log("----------------------------")
console.time("TRUE test1.1")
i=0;
for(;i<100000000;i=i+1){
true === true ? 1 : 0;
}
console.timeEnd("TRUE test1.1")
console.time("FALSE test2.1")
i=0;
for(;i<100000000;i=i+1){
false === true ? 1 : 0;
}
console.timeEnd("FALSE test2.1")
console.log("----------------------------")
console.time("TRUE test3")
i=0;
for(;i<100000000;i=i+1){
true | 0;
}
console.timeEnd("TRUE test3")
console.time("FALSE test4")
i=0;
for(;i<100000000;i=i+1){
false | 0;
}
console.timeEnd("FALSE test4")
console.log("----------------------------")
console.time("TRUE test5")
i=0;
for(;i<100000000;i=i+1){
true * 1;
}
console.timeEnd("TRUE test5")
console.time("FALSE test6")
i=0;
for(;i<100000000;i=i+1){
false * 1;
}
console.timeEnd("FALSE test6")
console.log("----------------------------")
console.time("TRUE test7")
i=0;
for(;i<100000000;i=i+1){
true & 1;
}
console.timeEnd("TRUE test7")
console.time("FALSE test8")
i=0;
for(;i<100000000;i=i+1){
false & 1;
}
console.timeEnd("FALSE test8")
console.log("----------------------------")
console.time("TRUE test9")
i=0;
for(;i<100000000;i=i+1){
+true;
}
console.timeEnd("TRUE test9")
console.time("FALSE test10")
i=0;
for(;i<100000000;i=i+1){
+false;
}
console.timeEnd("FALSE test10")
console.log("----------------------------")
console.time("TRUE test9.1")
i=0;
for(;i<100000000;i=i+1){
0+true;
}
console.timeEnd("TRUE test9.1")
console.time("FALSE test10.1")
i=0;
for(;i<100000000;i=i+1){
0+false;
}
console.timeEnd("FALSE test10.1")
console.log("----------------------------")
console.time("TRUE test9.2")
i=0;
for(;i<100000000;i=i+1){
-true*-1;
}
console.timeEnd("TRUE test9.2")
console.time("FALSE test10.2")
i=0;
for(;i<100000000;i=i+1){
-false*-1;
}
console.timeEnd("FALSE test10.2")
console.log("----------------------------")
console.time("TRUE test9.3")
i=0;
for(;i<100000000;i=i+1){
true-0;
}
console.timeEnd("TRUE test9.3")
console.time("FALSE test10.3")
i=0;
for(;i<100000000;i=i+1){
false-0;
}
console.timeEnd("FALSE test10.3")
console.log("----------------------------")
console.time("TRUE test11")
i=0;
for(;i<100000000;i=i+1){
Number(true);
}
console.timeEnd("TRUE test11")
console.time("FALSE test12")
i=0;
for(;i<100000000;i=i+1){
Number(false);
}
console.timeEnd("FALSE test12")
console.log("----------------------------")
console.time("TRUE test13")
i=0;
for(;i<100000000;i=i+1){
true + 0;
}
console.timeEnd("TRUE test13")
console.time("FALSE test14")
i=0;
for(;i<100000000;i=i+1){
false + 0;
}
console.timeEnd("FALSE test14")
console.log("----------------------------")
console.time("TRUE test15")
i=0;
for(;i<100000000;i=i+1){
true ^ 0;
}
console.timeEnd("TRUE test15")
console.time("FALSE test16")
i=0;
for(;i<100000000;i=i+1){
false ^ 0;
}
console.timeEnd("FALSE test16")
console.log("----------------------------")
console.time("TRUE test17")
i=0;
for(;i<100000000;i=i+1){
true ^ 0;
}
console.timeEnd("TRUE test17")
console.time("FALSE test18")
i=0;
for(;i<100000000;i=i+1){
false ^ 0;
}
console.timeEnd("FALSE test18")
console.log("----------------------------")
console.time("TRUE test19")
i=0;
for(;i<100000000;i=i+1){
true >> 0;
}
console.timeEnd("TRUE test19")
console.time("FALSE test20")
i=0;
for(;i<100000000;i=i+1){
false >> 0;
}
console.timeEnd("FALSE test20")
console.log("----------------------------")
console.time("TRUE test21")
i=0;
for(;i<100000000;i=i+1){
true >>> 0;
}
console.timeEnd("TRUE test21")
console.time("FALSE test22")
i=0;
for(;i<100000000;i=i+1){
false >>> 0;
}
console.timeEnd("FALSE test22")
console.log("----------------------------")
console.time("TRUE test23")
i=0;
for(;i<100000000;i=i+1){
true << 0;
}
console.timeEnd("TRUE test23")
console.time("FALSE test24")
i=0;
for(;i<100000000;i=i+1){
false << 0;
}
console.timeEnd("FALSE test24")
console.log("----------------------------")
console.time("TRUE test25")
i=0;
for(;i<100000000;i=i+1){
~~true;
}
console.timeEnd("TRUE test25")
console.time("FALSE test26")
i=0;
for(;i<100000000;i=i+1){
~~false;
}
console.timeEnd("FALSE test26")
console.log("----------------------------")
console.time("TRUE test25.1")
i=0;
for(;i<100000000;i=i+1){
~true*-1-1;
}
console.timeEnd("TRUE test25.1")
console.time("FALSE test26.1")
i=0;
for(;i<100000000;i=i+1){
~false*-1-1;
}
console.timeEnd("FALSE test26.1")
console.log("----------------------------")
console.time("TRUE test27")
i=0;
for(;i<100000000;i=i+1){
true/1;
}
console.timeEnd("TRUE test27")
console.time("FALSE test28")
i=0;
for(;i<100000000;i=i+1){
false/1;
}
console.timeEnd("FALSE test28")
结果
TRUE test1: 93.301ms
FALSE test2: 102.854ms
----------------------------
TRUE test1.1: 118.979ms
FALSE test2.1: 119.061ms
----------------------------
TRUE test3: 97.265ms
FALSE test4: 108.389ms
----------------------------
TRUE test5: 85.854ms
FALSE test6: 87.449ms
----------------------------
TRUE test7: 83.126ms
FALSE test8: 84.992ms
----------------------------
TRUE test9: 99.683ms
FALSE test10: 87.080ms
----------------------------
TRUE test9.1: 85.587ms
FALSE test10.1: 86.050ms
----------------------------
TRUE test9.2: 85.883ms
FALSE test10.2: 89.066ms
----------------------------
TRUE test9.3: 86.722ms
FALSE test10.3: 85.187ms
----------------------------
TRUE test11: 86.245ms
FALSE test12: 85.808ms
----------------------------
TRUE test13: 84.192ms
FALSE test14: 84.173ms
----------------------------
TRUE test15: 81.575ms
FALSE test16: 81.699ms
----------------------------
TRUE test17: 81.979ms
FALSE test18: 81.599ms
----------------------------
TRUE test19: 81.578ms
FALSE test20: 81.452ms
----------------------------
TRUE test21: 115.886ms
FALSE test22: 88.935ms
----------------------------
TRUE test23: 82.077ms
FALSE test24: 81.822ms
----------------------------
TRUE test25: 81.904ms
FALSE test26: 82.371ms
----------------------------
TRUE test25.1: 82.319ms
FALSE test26.1: 96.648ms
----------------------------
TRUE test27: 89.943ms
FALSE test28: 83.646ms
其他回答
let integerVariable = booleanVariable * 1;
当JavaScript期望一个数字值但接收到一个布尔值时，它会将该布尔值转换为一个数字:true和false分别转换为1和0。所以你可以利用这个;
Var t = true; Var f = false; console.log (t * 1);// t*1 == 1 console.log (f * 1);// f*1 === 0 console.log (+ t);// 0+t === 1或缩短为+t === 1 console.log (+ f);//0+f === 0或缩短为+f === 0
进一步阅读Javascript权威指南第3.8章的类型转换。
我已经测试了所有这些例子，我做了一个基准测试，最后我建议你选择较短的一个，它不会影响性能。
运行在Ubuntu服务器14.04,nodejs v8.12.0 - 26/10/18
let i = 0;
console.time("TRUE test1")
i=0;
for(;i<100000000;i=i+1){
true ? 1 : 0;
}
console.timeEnd("TRUE test1")
console.time("FALSE test2")
i=0;
for(;i<100000000;i=i+1){
false ? 1 : 0;
}
console.timeEnd("FALSE test2")
console.log("----------------------------")
console.time("TRUE test1.1")
i=0;
for(;i<100000000;i=i+1){
true === true ? 1 : 0;
}
console.timeEnd("TRUE test1.1")
console.time("FALSE test2.1")
i=0;
for(;i<100000000;i=i+1){
false === true ? 1 : 0;
}
console.timeEnd("FALSE test2.1")
console.log("----------------------------")
console.time("TRUE test3")
i=0;
for(;i<100000000;i=i+1){
true | 0;
}
console.timeEnd("TRUE test3")
console.time("FALSE test4")
i=0;
for(;i<100000000;i=i+1){
false | 0;
}
console.timeEnd("FALSE test4")
console.log("----------------------------")
console.time("TRUE test5")
i=0;
for(;i<100000000;i=i+1){
true * 1;
}
console.timeEnd("TRUE test5")
console.time("FALSE test6")
i=0;
for(;i<100000000;i=i+1){
false * 1;
}
console.timeEnd("FALSE test6")
console.log("----------------------------")
console.time("TRUE test7")
i=0;
for(;i<100000000;i=i+1){
true & 1;
}
console.timeEnd("TRUE test7")
console.time("FALSE test8")
i=0;
for(;i<100000000;i=i+1){
false & 1;
}
console.timeEnd("FALSE test8")
console.log("----------------------------")
console.time("TRUE test9")
i=0;
for(;i<100000000;i=i+1){
+true;
}
console.timeEnd("TRUE test9")
console.time("FALSE test10")
i=0;
for(;i<100000000;i=i+1){
+false;
}
console.timeEnd("FALSE test10")
console.log("----------------------------")
console.time("TRUE test9.1")
i=0;
for(;i<100000000;i=i+1){
0+true;
}
console.timeEnd("TRUE test9.1")
console.time("FALSE test10.1")
i=0;
for(;i<100000000;i=i+1){
0+false;
}
console.timeEnd("FALSE test10.1")
console.log("----------------------------")
console.time("TRUE test9.2")
i=0;
for(;i<100000000;i=i+1){
-true*-1;
}
console.timeEnd("TRUE test9.2")
console.time("FALSE test10.2")
i=0;
for(;i<100000000;i=i+1){
-false*-1;
}
console.timeEnd("FALSE test10.2")
console.log("----------------------------")
console.time("TRUE test9.3")
i=0;
for(;i<100000000;i=i+1){
true-0;
}
console.timeEnd("TRUE test9.3")
console.time("FALSE test10.3")
i=0;
for(;i<100000000;i=i+1){
false-0;
}
console.timeEnd("FALSE test10.3")
console.log("----------------------------")
console.time("TRUE test11")
i=0;
for(;i<100000000;i=i+1){
Number(true);
}
console.timeEnd("TRUE test11")
console.time("FALSE test12")
i=0;
for(;i<100000000;i=i+1){
Number(false);
}
console.timeEnd("FALSE test12")
console.log("----------------------------")
console.time("TRUE test13")
i=0;
for(;i<100000000;i=i+1){
true + 0;
}
console.timeEnd("TRUE test13")
console.time("FALSE test14")
i=0;
for(;i<100000000;i=i+1){
false + 0;
}
console.timeEnd("FALSE test14")
console.log("----------------------------")
console.time("TRUE test15")
i=0;
for(;i<100000000;i=i+1){
true ^ 0;
}
console.timeEnd("TRUE test15")
console.time("FALSE test16")
i=0;
for(;i<100000000;i=i+1){
false ^ 0;
}
console.timeEnd("FALSE test16")
console.log("----------------------------")
console.time("TRUE test17")
i=0;
for(;i<100000000;i=i+1){
true ^ 0;
}
console.timeEnd("TRUE test17")
console.time("FALSE test18")
i=0;
for(;i<100000000;i=i+1){
false ^ 0;
}
console.timeEnd("FALSE test18")
console.log("----------------------------")
console.time("TRUE test19")
i=0;
for(;i<100000000;i=i+1){
true >> 0;
}
console.timeEnd("TRUE test19")
console.time("FALSE test20")
i=0;
for(;i<100000000;i=i+1){
false >> 0;
}
console.timeEnd("FALSE test20")
console.log("----------------------------")
console.time("TRUE test21")
i=0;
for(;i<100000000;i=i+1){
true >>> 0;
}
console.timeEnd("TRUE test21")
console.time("FALSE test22")
i=0;
for(;i<100000000;i=i+1){
false >>> 0;
}
console.timeEnd("FALSE test22")
console.log("----------------------------")
console.time("TRUE test23")
i=0;
for(;i<100000000;i=i+1){
true << 0;
}
console.timeEnd("TRUE test23")
console.time("FALSE test24")
i=0;
for(;i<100000000;i=i+1){
false << 0;
}
console.timeEnd("FALSE test24")
console.log("----------------------------")
console.time("TRUE test25")
i=0;
for(;i<100000000;i=i+1){
~~true;
}
console.timeEnd("TRUE test25")
console.time("FALSE test26")
i=0;
for(;i<100000000;i=i+1){
~~false;
}
console.timeEnd("FALSE test26")
console.log("----------------------------")
console.time("TRUE test25.1")
i=0;
for(;i<100000000;i=i+1){
~true*-1-1;
}
console.timeEnd("TRUE test25.1")
console.time("FALSE test26.1")
i=0;
for(;i<100000000;i=i+1){
~false*-1-1;
}
console.timeEnd("FALSE test26.1")
console.log("----------------------------")
console.time("TRUE test27")
i=0;
for(;i<100000000;i=i+1){
true/1;
}
console.timeEnd("TRUE test27")
console.time("FALSE test28")
i=0;
for(;i<100000000;i=i+1){
false/1;
}
console.timeEnd("FALSE test28")
结果
TRUE test1: 93.301ms
FALSE test2: 102.854ms
----------------------------
TRUE test1.1: 118.979ms
FALSE test2.1: 119.061ms
----------------------------
TRUE test3: 97.265ms
FALSE test4: 108.389ms
----------------------------
TRUE test5: 85.854ms
FALSE test6: 87.449ms
----------------------------
TRUE test7: 83.126ms
FALSE test8: 84.992ms
----------------------------
TRUE test9: 99.683ms
FALSE test10: 87.080ms
----------------------------
TRUE test9.1: 85.587ms
FALSE test10.1: 86.050ms
----------------------------
TRUE test9.2: 85.883ms
FALSE test10.2: 89.066ms
----------------------------
TRUE test9.3: 86.722ms
FALSE test10.3: 85.187ms
----------------------------
TRUE test11: 86.245ms
FALSE test12: 85.808ms
----------------------------
TRUE test13: 84.192ms
FALSE test14: 84.173ms
----------------------------
TRUE test15: 81.575ms
FALSE test16: 81.699ms
----------------------------
TRUE test17: 81.979ms
FALSE test18: 81.599ms
----------------------------
TRUE test19: 81.578ms
FALSE test20: 81.452ms
----------------------------
TRUE test21: 115.886ms
FALSE test22: 88.935ms
----------------------------
TRUE test23: 82.077ms
FALSE test24: 81.822ms
----------------------------
TRUE test25: 81.904ms
FALSE test26: 82.371ms
----------------------------
TRUE test25.1: 82.319ms
FALSE test26.1: 96.648ms
----------------------------
TRUE test27: 89.943ms
FALSE test28: 83.646ms
+ ! !允许你对一个变量应用这个，即使它是未定义的:
+!!undefined // 0
+!!false // 0
+!!true // 1
+!!(<boolean expression>) // 1 if it evaluates to true, 0 otherwise
我今天偶然发现了这条近路。
~ ~(真正的)
~ ~(假)
比我聪明得多的人可以解释:
http://james.padolsey.com/javascript/double-bitwise-not/
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