1. Js indicates that the exact format of the number is [-2^53,2^53], but some operators in JS have a range of [-2^31,2^ 31-1]
ToString (n), where n=[2,36]
3.0/0 = NaN
4. Functions are data types that can be stored in variables, arrays, and objects and passed as arguments to other functions
5. Addition
(1) If the object type is Date, toString() is called;
(2) Otherwise, if valueOf() returns a primitive type, valueOf() of the object is called;
(3) In other cases (if valueOf() does not exist or does not return a primitive type), the toString() method is called, most of the time using this conversion.
Note: JavaScript uses its join(‘,’) method when an array is converted to its original type, for example [1,5,6] is “1,5,6”. The primitive type of a normal JavaScript object {} is “[object object]”.
Example 1: numbers and strings
var result = 1 + “5”; 15 “/ /”
Example 2: Numbers and arrays
var result = [1, 3, 5] + 1; / / “1,3,51”
Example 3: Numeric and Boolean types
var result = 10 + true; / / 11
Example 4: Numbers and objects
var result = 15 + {}; // “15[object Object]”
Example 5: numbers and NULL
var result = 8 + null; // 8.
8 + 0 (add numbers) 8 Since the operands are neither objects nor strings, NULL is converted to a number and the sum of the numbers is evaluated.
Example 6: String and NULL
var result = “queen” + null; // “queennull” parse:
“Queen” + null (since the first operand is a string, null is converted to the string “null” based on Rule 2) “queen” + “null” (string concatenation) “Queennull” Since the first operand is a string, null is converted to a string, Then string concatenation is performed.
Example 7: numbers and undefined
var result = 12 + undefined; // NaN
Resolution:
12 + undefined (since operands are not objects or strings, convert undefined to NaN based on rule 3) 12 + NaN (add numbers) NaN
6. The in operator
7. The delete operator
8. The with statement (not recommended)
