Something you have to know about JavaScript.

The template string 1, JavaScript does not distinguish between integers and floating-point numbers, is uniformly represented by number.

2. NaN This special number is not equal to all other values, including itself:

Nan===nan; False

The only way to judge NaN is through the isNaN() function:

IsNaN (NaN); True

3 null . Represents an "empty" value, which, 0 unlike an empty string ‘‘ , 0 is a numeric value that ‘‘ represents a string of length 0 and null represents "null". The undefined expression value is undefined.

4. JavaScript arrays can include arbitrary data types.

[1, 2, 3.14, ' Hello ', NULL, true];

Another way to create an array is through a Array() function:

New Array (1, 2, 3); Array created [1, 2, 3]

5. The way to enable strict mode is to write on the first line of the JavaScript code:

6, because the multi-line string to \n write up more trouble, so the latest ES6 standard added a multi-line string representation method, with anti-quote ' ... ' means:

' This is a multi-line string ';

The results of the operation are as follows:

7. Template string

To concatenate multiple strings, you can connect them with a + number:

var name = ' Xiaoming '; var age = 20;var message = ' Hello, ' + name + ', you are this year ' + Ages + ' old! '; alert (message);

If there are many variables that need to be connected, + it is more troublesome to use the number. It is convenient to use ES6 template strings.

var name = ' Xiaoming '; var age = 20;var message = ' Hello, ${name}, you ${age} year old! '; alert (message);

The result is exactly the same:

8. JavaScript provides some common methods for strings, note that calling these methods does not alter the contents of the original string, but instead returns a new string:

　　toUpperCase()Turn a string into uppercase;

　　toLowerCase()Turn a string into lowercase;

Something you have to know about JavaScript.