How to set the default parameters of JavaScript Functions

1. We can define a function similar to this in PHP or C/C ++:
2. Function func (INT num = 1 ){...}
4. If there is no parameter when you call func, the default value is 1, which cannot be directly written in Javascript. to implement similar functions, you can use the arguments object of javascript:
6. PHP programmer site
8. This object represents the function being executed and the parameters of the function that calls it.
10. The usage is as follows: PhP programmer's house
12. [Function.] arguments [N]
14. PHP programmer site
17. Function
19. Optional. Name of the function object currently being executed.
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26. Required. The index of the parameter value starting from 0 to be passed to the function object.
28. The following methods can be used to meet our requirements:
30. WWW ~ Phperz ~ Com
33. Reference content is as follows:
34. <Script language = JavaScript>
35. Function writestr ()
36. {
37. VaR STR = arguments [0] | "I am the default parameter ";
38. Return STR;
39. }
40. Document. Write (writestr () + "<br> ");
41. Document. Write (writestr ("I am the set parameter") + "<br> ");
42. </SCRIPT>
46. In this example, we define only one default parameter. If you want to define two parameters, you can add one more parameter to the function.
51. VaR str2 = arguments [0] | "I am the default parameter 2.
53. PHP programmer's house
56. Note: This method has a problem, that is, when the parameter is 0, false, or null, it is invalid.