JS字串常用方法（自） 8 字串查詢

字串查詢方法有6個，startswith(searchstring,position)， endswith(searchstring,length)， search(regexp)， indexof(searchvalue,fromindex)， lastindexof(searchvalue,fromindex)， includes(searchstring,position)

startswith(searchstring,position)，endswith(searchstring,length)

search(regexp)

indexof(searchvalue,fromindex)，lastindexof(searchvalue,fromindex)

includes(searchstring,position)

從fromindex往左查，所以'hello world, hello world'.lastindexof('llo',3)的結果是2關於找索引值的函式，找到就是返回的找到的索引，沒找到就返回-1startswith()方法的第二個引數表示要查詢的位置，endswith()方法的第二個引數表示指定字串搜尋的長度。

1

doctype html
>
2<
html 
lang
="en"
>
3<
head
>
4<
meta 
charset
="utf-8"
>
5<
title
>startswith()
title
>
6head
>
7<
body
>815
<
script
>
16var
str ="
to be, or not to be, that is the question.";
1718
console.log(str.startswith(
"to be
"));         
//true
19console.log(str.startswith(
"not to be
"));     
//false
20console.log(str.startswith(
"not to be", 
10)); 
//true
21script
>
22body
>
23html
>

1

doctype html
>
2<
html 
lang
="en"
>
3<
head
>
4<
meta 
charset
="utf-8"
>
5<
title
>endswith()
title
>
6head
>
7<
body
>824
<
script
>
25var
str ="
to be, or not to be, that is the question.";
2627
console.log( str.endswith(
"question.
") );  
//true
28console.log( str.endswith(
"to be
") );      
//false
29console.log( str.endswith(
"to be", 
19) );  
//true
30script
>
31body
>
32html
>

doctype html
>
<
html 
lang
="en"
>
<
head
>
<
meta 
charset
="utf-8"
>
<
title
>search()
title
>
head
>
<
body
>
<
script
>
varstr ="
hey jude";
varre =/
[a-z]/g;
varre2 =/
[.]/
g;    console.log(str.search(re)); 
//returns 4, which is the index of the first capital letter "j"
console.log(str.search(re2)); 
//returns -1 cannot find '.' dot punctuation
script
>
body
>
html
>

doctype html
>
<
html 
lang
="en"
>
<
head
>
<
meta 
charset
="utf-8"
>
<
title
>indexof()
title
>
head
>
<
body
>
<
script
>
console.log(
'hello world
'.indexof(
'llo
'));
console.log(
'hello world
'.indexof(
'llo',
3));
script
>
body
>
html
>

doctype html
>
<
html 
lang
="en"
>
<
head
>
<
meta 
charset
="utf-8"
>
<
title
>lastindexof()
title
>
head
>
<
body
>
<
script
>
console.log(
'hello world, hello world
'.lastindexof(
'llo
'));
//15
console.log(
'hello world, hello world
'.lastindexof(
'llo',
3));//2
script
>
body
>
html
>

doctype html
>
<
html 
lang
="en"
>
<
head
>
<
meta 
charset
="utf-8"
>
<
title
>includes()
title
>
head
>
<
body
>
<
script
>
varstr ='
to be, or not to be, that is the question.';
console.log(str.includes(
'to be
'));       
//true
console.log(str.includes(
'question
'));    
//true
console.log(str.includes(
'nonexistent
')); 
//false
console.log(str.includes(
'to be', 
1));    
//false
console.log(str.includes(
'to be
'));       
//false
script
>
body
>
html
>

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