ReferenceError: "x" is not defined
JavaScript ็ใvariable is not definedใไพๅคๆๅจๆ่ๅ่ไบไธๅไธๅญๅจ็่ฎๆธๆ็ผ็ ใ
่จๆฏ
ReferenceError: "x" is not defined๏ผๅบๆผ V8 & Firefox๏ผ ReferenceError: Can't find variable: x๏ผSafari๏ผ
้ฏ่ชค้กๅ
ๅช่ฃกๅบ้ฏไบ๏ผ
ๆ่ๅ่ไบไธๅไธๅญๅจ็่ฎๆธใ้ๅ่ฎๆธ้่ฆ่ขซๅฎฃๅ๏ผๆ่ ไฝ ้่ฆ็ขบไฟๅฎๅจไฝ ็ฎๅ็่ ณๆฌๆไฝ็จๅไธญๆฏๅฏ็จ็ใ
ๅ่จป๏ผ
็ถ่ผๅ
ฅไธๅๅฝๅผๅบซ๏ผไพๅฆ jQuery๏ผๆ๏ผ่ซ็ขบไฟๅจๅญๅๅฝๅผๅบซ่ฎๆธ๏ผไพๅฆใ$ใ๏ผไนๅๅฐฑๅทฒ็ถ่ผๅ
ฅๅฎใ่ซๅฐ่ผๅ
ฅๅฝๅผๅบซ็ <script> ๅ
็ด ๆพๅจไฝฟ็จๅฎ็็จๅผ็ขผไนๅใ
็ฏไพ
่ฎๆธๆชๅฎฃๅ
foo.substring(1); // ReferenceError: foo is not defined
ใfooใ่ฎๆธๆฒๆๅจไปปไฝๅฐๆน่ขซๅฎ็พฉใๅฎ้่ฆๆฏไธๅๅญไธฒ๏ผ้ๆจฃ String.prototype.substring() ๆนๆณๆ่ฝ้ไฝใ
const foo = "bar";
foo.substring(1); // "ar"
้ฏ่ชค็ไฝ็จๅ
ไธๅ่ฎๆธ้่ฆๅจ็ฎๅ็ๅท่กไธไธๆไธญๅฏ็จใๅจๅฝๅผๅ ง้จๅฎ็พฉ็่ฎๆธ็กๆณๅพๅฝๅผๅค้จ็ไปปไฝๅฐๆนๅญๅ๏ผๅ ็บ่ฉฒ่ฎๆธๅชๅจๅฝๅผ็ไฝ็จๅไธญ่ขซๅฎ็พฉใ
function numbers() {
const num1 = 2;
const num2 = 3;
return num1 + num2;
}
console.log(num1); // ReferenceError num1 is not defined.
็ถ่๏ผไธๅๅฝๅผๅฏไปฅๅญๅๅจๅ ถๅฎ็พฉ็ไฝ็จๅๅ งๆๅฎ็พฉ็ๆๆ่ฎๆธๅๅฝๅผใๆๅฅ่ฉฑ่ชช๏ผๅจๅ จๅไฝ็จๅไธญๅฎ็พฉ็ๅฝๅผๅฏไปฅๅญๅๅจๅ จๅไฝ็จๅไธญๅฎ็พฉ็ๆๆ่ฎๆธใ
const num1 = 2;
const num2 = 3;
function numbers() {
return num1 + num2;
}
console.log(numbers()); // 5