JavaScript資料型別強制轉換

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基本資料：number, boolean, undefined, null, string;

引用資料：object;

當0.000…01，小數點後大於等於7位時會自動轉換成科學計數法

當20000…00，當整數部分大於等於22位時會自動轉換成科學計數法。

console.log(number(1));        //1

console.log(number(1e-7));    //1e-7
console.log(number(0b111));  //7
console.log(number(nan));   //nan

console.log(number(true));  //1

console.log(number(false)); //0

console.log(number(undefined)); //nan

console.log(number(null));    //0

//數字字串

console.log(number("123"));   //123
console.log(number("-123"));  //-123
console.log(number("12.3"));  
console.log(number("1e-7"));  //1e-7
console.log(number("0xff"));  //255
console.log(number("00123")); //123	
console.log(number("   123")); //123
console.log(number("\t\n123")); //123

//數字+字元或全字元字串

console.log(number('a123'));  //nan
console.log(number("false")); //nan
console.log(number("a123"));  //nan

//空串或者空格字串

console.log(number("\t\n"));   //0
console.log(number("  "));     //0
console.log(number(""));       //0

console.log(number({}));  //nan

console.log(number([1])); //1
console.log(number([1,2]));  //nan
cosole.log(number());    //0

無引數y時：

console.log(parseint(123));   //123

console.log(parseint(1e-7));  //1
console.log(parseint(0xff));  //255
console.log(parseint(nan));   //nan
console.log(parseint(0.00001)); //0

console.log(parseint(true));  //nan

console.log(parseint(false)); //nan
console.log(parseint(undefined)); //nan
console.log(parseint(null));    //nan

console.log(parseint(""));   //nan

console.log(parseint("-123"));  //-123
console.log(parseint("  "));  //nan
console.log(parseint("\t\n"));   //nan
console.log(parseint("a123")); //nan
console.log(parseint("123a")); //123

console.log(parseint());   //"[object object]"->nan

console.log(parseint());      //""->nan
console.log(parseint([1,2]));   //"1,2"->//1

console.log(parseint("f",2));   //nan

console.log(parseint("11f",2);  //3
console.log(parseint("123",37)); //nan
console.log(parseint("0xff",0));  //255
console.log(parseint("0xff",nan)); //255
console.log(parseint("ff",));  //nan

console.log(parsefloat(0xff));  //255

console.log(parsefloat("0xff"));  //0  
console.log(parseint("0xff"));   //255  個人猜測parseint(x,y)有y的存在所以能正確輸出
console.log(parsefloat(1e22));   //1e22
console.log(parsefloat(1e-7));   //1e-7
console.log(parsefloat("00123"));  //123
console.log(parsefloat(" "));     //nan

console.log(string(null));  //"null"

console.log(0xff.tostring(2));  //"11111111"
console.log(oxff.tostring()); //"255" 不填預設10進製

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