JavaScript的Async和Sync——一个简单的code
JavaScript 是一种解释性语言。
Python也是一种解释性语言。
对于解释性语言，需要了解该语言的Integrated Development Environment，比如命令行。
Python中的sync，
for x in [1,2,3,4,5,6,7,8,9,0]
y = 0
while y < 1000000:
y += 1
print x
JavaScript中的Async:
fs = require('fs');
fs.writeFile('./write.txt', 'Hello World!', function(err){
if (err) throw err;
console.log('Oh, it writes successfully!');
console.log("I'm async and I will show later");
}
console.log(" HAHA,In fact, I'm sync and I will show earlier");
分别用Python和node来运行上面两段代码，可以感受下区别。
个人觉得，回调回调，回过头来再调用。
有句话，“你们给我等着，我还会回来的”，个人以为是差不多的Async。
// // *** An anonymous function used as closure ***
var baz;
(function() {
var foo = 10， bar = 2;
baz = function() {
return foo*bar;
};
})();
// // Javascript has ***function level*** scope.
// // * This means a variable defined within a function is ***NOT*** accessible ***outside*** of it.
try {
console.log(foo);
}
catch(err) {
console.log(err); //error
}
try {
console.log(bar);
}
catch(err) {
console.log(err); //error
}
// // Javascript has ***lexcially level*** scope， also called ***Static Scope***
// // * This means functions run in the scope they are ***defined in***, ***NOT*** the scope they are ***excuted in***.
console.log(baz());