Mutual conversion of strings and arrays in JS

Mutual conversion of strings and arrays in JS

In the morning, I read a JS interview question, which is described as follows: use var s1 = prompt ("Please input any string", "") to obtain user input.

String, try programming to "reverse" the user input string, and output the string.

After thinking about it, the string object method does not implement inversion, but there are arrays, so the conversion between strings and arrays is considered.

The built-in objects in JS include String objects and Array objects. These two objects can be implemented through their methods.

Converted. For String objects, the attribute and method of String operations are provided. For Array objects, the attribute and method of Array operations are provided.

Method. Therefore, it is easy to implement the above interview questions.

First, we can see that the string is converted to an array.

Split () method in String object

The function of the preceding method is to cut a string into several segments and return an array. That is to say, a string can be converted into a numerical value. For example:

StrObj. split (split number). The parameter is a string of the split number. The specified split number is used to cut the string into several segments.

Instance:

// Specify the day of the week to be output. // define a weekly string var str = "Sunday, Monday, Tuesday, Wednesday, Thursday, Saturday "; // create a Date object var today = new Date (); // use the getDay () method of the today object var week = today. getDay (); // splits the week string into an array var arr = str. split (","); document. write ("type:" + typeof (arr) + ", the first element of the array is:" + arr [0] + ""); // output result document. write ("today is:" + arr [week]);

The output result is: object type. The first element of the array is Sunday.

Today is: Friday

Second, let's look at array conversion to string and array element inversion.

Join () method of Array object

The function of the preceding method is to convert an array into a string. For example, arrObj. join (connection number) links an array with the specified connection number into a word.

String.

Instance:

Var arr = ["a", "B", "c"]; var str = arr. join ("-"); document. write ("type:" + typeof (str) + ", string:" + str );

The output result is: string type, and the string is a-B-c.

Array object reverse () method

The function of the preceding method is to reverse the order of elements in the array. For example, arrObj. reverse ().

Instance:

var arr=["a","b","c"];arr.reverse();document.write(arr);

The output result is: c, B,

Finally, let's look at the implementation code of the interview question:

/* Use var s1 = prompt ("enter any string", "") to obtain the user-input string, and try programming to "reverse" the user-input string ", and output the string. * /// Accept the string var s1 = prompt ("enter any string", ""); // convert the string to an array var arr = s1.split (""); // use the array object's reverse () method to reverse the arr. reverse (); // use the join () method of the array to convert to the string var str = arr. join (""); document. write (str );

Implementation result: