属性只有一个值的这类 html 属性是怎么回事，该如何设置值；比如：checked = “checked” vs checked = true
参考链接：https://stackoverflow.com/questions/10650233/checked-checked-vs-checked-true
问：
1 What is the difference between the below two usages? 2 3 document.getElementById('myRadio').checked = "checked"; 4 and 5 6 document.getElementById('myRadio').checked = true; 7 For me, both are behaving the same way. But, I am just curious to know why there exist two methods to do the same. 8 9 Which one will be the ideal usage? I need to support IE7 and higher versions.
答：
1 document.getElementById('myRadio').checked is a boolean value. It should be true or false 2 3 document.getElementById('myRadio').checked = "checked"; casts the string to a boolean, which is true. 4 5 document.getElementById('myRadio').checked = true; just assigns true without casting. 6 7 Use true as it is marginally more efficient and is more intention revealing to maintainers.
document.getElementById（'myRadio'）。checked是一个布尔值。 这应该是真的或假的
document.getElementById（'myRadio'）。checked =“checked”; 将字符串转换为布尔值，这是正确的。
document.getElementById（'myRadio'）。checked = true; 只是分配true而不投射。
使用true，因为它的效率稍微高一点，而且更有意向维护者展示。
所以设置这种单属性的值为 true 或 false 就对了。
