<\/span><\/h2>\n\n\n\nPh\u01b0\u01a1ng th\u1ee9c indexOf()<\/code>\u00a0<\/strong>tr\u1ea3 v\u1ec1 v\u1ecb tr\u00ed xu\u1ea5t hi\u1ec7n \u0111\u1ea7u ti\u00ean c\u1ee7a chu\u1ed7i c\u1ea7n t\u00ecm trong chu\u1ed7i l\u1edbn h\u01a1n.<\/p>\n\n\n\nV\u00ed d\u1ee5:<\/h3>\n\n\n\nvar str = \"Ki\u1ebfn c\u00e0ng c\u00f3 nhi\u1ec1u b\u00e0i vi\u1ebft v\u1ec1 HTML, CSS v\u00e0 JavaScript, ngo\u00e0i ra c\u00f2n c\u00f3 nhi\u1ec1u b\u00e0i v\u1ec1 PHP - MySQL n\u1eefa\";\nvar pos = str.indexOf(\"nhi\u1ec1u\");<\/code><\/pre>\n\n\n\nPh\u01b0\u01a1ng th\u1ee9c lastIndexOf()<\/code> tr\u1ea3 v\u1ec1 v\u1ecb tr\u00ed xu\u1ea5t hi\u1ec7n cu\u1ed1i c\u00f9ng c\u1ee7a chu\u1ed7i c\u1ea7n t\u00ecm trong chu\u1ed7i l\u1edbn h\u01a1n.<\/p>\n\n\n\nV\u00ed d\u1ee5:<\/h3>\n\n\n\nvar str = \"Ki\u1ebfn c\u00e0ng c\u00f3 nhi\u1ec1u b\u00e0i vi\u1ebft v\u1ec1 HTML, CSS v\u00e0 JavaScript, ngo\u00e0i ra c\u00f2n c\u00f3 nhi\u1ec1u b\u00e0i v\u1ec1 PHP - MySQL n\u1eefa\";\nvar pos = str.lastIndexOf(\"nhi\u1ec1u\");<\/code><\/pre>\n\n\n\nC\u1ea3 hai ph\u01b0\u01a1ng th\u1ee9c indexOf()<\/code> v\u00e0 lastIndexOf()<\/code> \u0111\u1ec1u tr\u1ea3 v\u1ec1 k\u1ebft qu\u1ea3 -1 n\u1ebfu chu\u1ed7i c\u1ea7n t\u00ecm kh\u00f4ng th\u1ea5y.<\/p>\n\n\n\nJavaScript \u0111\u1ebfm v\u1ecb tr\u00ed b\u1eaft \u0111\u1ea7u t\u1eeb zero (0).<\/p>\n\n\n\n
0 l\u00e0 v\u1ecb tr\u00ed \u0111\u1ea7u ti\u00ean trong m\u1ed9t chu\u1ed7i, 1 l\u00e0 v\u1ecb tr\u00ed th\u1ee9 hai, 2 l\u00e0 v\u1ecb tr\u00ed th\u1ee9 3 …<\/p>\n\n\n\n
C\u1ea3 hai ph\u01b0\u01a1ng ph\u00e1p ch\u1ea5p nh\u1eadn m\u1ed9t tham s\u1ed1 th\u1ee9 hai l\u00e0 v\u1ecb tr\u00ed kh\u1edfi \u0111\u1ea7u cho t\u00ecm ki\u1ebfm.<\/p>\n\n\n\n
\n\n\n\n<\/span>T\u00ecm ki\u1ebfm chu\u1ed7i trong chu\u1ed7i<\/span><\/h2>\n\n\n\nPh\u01b0\u01a1ng th\u1ee9c search()<\/code>\u00a0t\u00ecm ki\u1ebfm m\u1ed9t chu\u1ed7i v\u1edbi gi\u00e1 tr\u1ecb \u0111\u01b0\u1ee3c ch\u1ec9 \u0111\u1ecbnh v\u00e0 tr\u1ea3 v\u1ec1 v\u1ecb tr\u00ed c\u1ee7a chu\u1ed7i tr\u00f9ng kh\u1edbp.<\/p>\n\n\n\nV\u00ed d\u1ee5:<\/h3>\n\n\n\nvar str = \"Ki\u1ebfn c\u00e0ng c\u00f3 nhi\u1ec1u b\u00e0i vi\u1ebft v\u1ec1 HTML, CSS v\u00e0 JavaScript, ngo\u00e0i ra c\u00f2n c\u00f3 nhi\u1ec1u b\u00e0i v\u1ec1 PHP - MySQL n\u1eefa\";\nvar pos = str.search(\"nhi\u1ec1u\");<\/code><\/pre>\n\n\n\n
\n\n\n\n<\/span>B\u1ea1n c\u1ea7n ch\u00fa \u00fd \u0111i\u1ec1u g\u00ec?<\/span><\/h2>\n\n\n\nHai ph\u01b0\u01a1ng th\u1ee9c indexOf()<\/code> v\u00e0 search()<\/code> l\u00e0 nh\u01b0 nhau.<\/p>\n\n\n\nCh\u00fang ch\u1ea5p nh\u1eadn c\u00f9ng m\u1ed9t \u0111\u1ed1i s\u1ed1 v\u00e0 tr\u1ea3 v\u1ec1 c\u00f9ng m\u1ed9t gi\u00e1 tr\u1ecb.<\/p>\n\n\n\n
M\u1eb7c d\u00f9 hai ph\u01b0\u01a1ng th\u1ee9c r\u1ea5t gi\u1ed1ng nhau, nh\u01b0ng search()<\/code> c\u00f3 th\u1ec3 l\u1ea5y gi\u00e1 tr\u1ecb t\u00ecm ki\u1ebfm m\u1ea1nh m\u1ebd h\u01a1n nhi\u1ec1u.<\/p>\n\n\n\nB\u1ea1n s\u1ebd h\u1ecdc v\u1ec1 s\u1ee9c m\u1ea1nh t\u00ecm ki\u1ebfm trong c\u00e1c ch\u01b0\u01a1ng v\u1ec1 c\u00e1c bi\u1ec3u th\u1ee9c th\u00f4ng th\u01b0\u1eddng.<\/p>\n\n\n\n
\n\n\n\n<\/span>Tr\u00edch xu\u1ea5t m\u1ed9t ph\u1ea7n chu\u1ed7i<\/span><\/h2>\n\n\n\nC\u00f3 3 ph\u01b0\u01a1ng th\u1ee9c \u0111\u1ec3 tr\u00edch xu\u1ea5t m\u1ed9t ph\u1ea7n chu\u1ed7i:<\/p>\n\n\n\n
- slice(start, end);<\/li>
- substring(start, end);<\/li>
- substr(start, length);<\/li><\/ul>\n\n\n\n
\n\n\n\n<\/span>Ph\u01b0\u01a1ng th\u1ee9c slice()<\/span><\/h2>\n\n\n\nslice()<\/code> <\/strong>tr\u00edch xu\u1ea5t m\u1ed9t ph\u1ea7n chu\u1ed7i v\u00e0 tr\u1ea3 v\u1ec1 ph\u1ea7n \u0111\u00e3 tr\u00edch xu\u1ea5t trong m\u1ed9t chu\u1ed7i m\u1edbi.<\/p>\n\n\n\nPh\u01b0\u01a1ng th\u1ee9c c\u00f3 2 tham s\u1ed1: ch\u1ec9 s\u1ed1 b\u1eaft \u0111\u1ea7u (v\u1ecb tr\u00ed), v\u00e0 ch\u1ec9 s\u1ed1 k\u1ebft th\u00fac (v\u1ecb tr\u00ed).<\/p>\n\n\n\n
V\u00ed d\u1ee5 d\u01b0\u1edbi \u0111\u00e2y c\u1eaft ra m\u1ed9t ph\u1ea7n c\u1ee7a chu\u1ed7i t\u1eeb v\u1ecb tr\u00ed 7 \u0111\u1ebfn v\u1ecb tr\u00ed 13.<\/p>\n\n\n\n
V\u00ed d\u1ee5:<\/h3>\n\n\n\nvar str = \"Apple, Banana, Kiwi\";\nvar res = str.slice(7,13);<\/code><\/pre>\n\n\n\nK\u1ebft qu\u1ea3 s\u1ebd l\u00e0: Banana<\/p>\n\n\n\n
N\u1ebfu \u0111\u1ed1i s\u1ed1 l\u00e0 s\u1ed1 \u00e2m, v\u1ecb tr\u00ed \u0111\u01b0\u1ee3c \u0111\u1ebfm t\u1eeb \u0111i\u1ec3m k\u1ebft th\u00fac c\u1ee7a chu\u1ed7i.<\/p>\n\n\n\n
V\u00ed d\u1ee5 d\u01b0\u1edbi \u0111\u00e2y c\u1eaft ra m\u1ed9t ph\u1ea7n c\u1ee7a chu\u1ed7i t\u1eeb v\u1ecb tr\u00ed -12 \u0111\u1ebfn -6.<\/p>\n\n\n\n
V\u00ed d\u1ee5:<\/h3>\n\n\n\nvar str = \"Apple, Banana, Kiwi\";\nvar res = str.slice(-12,-6);<\/code><\/pre>\n\n\n\nK\u1ebft qu\u1ea3 s\u1ebd l\u00e0: Banana<\/p>\n\n\n\n
N\u1ebfu b\u1ea1n b\u1ecf qua \u0111\u1ed1i s\u1ed1 th\u1ee9 hai, ph\u01b0\u01a1ng th\u1ee9c s\u1ebd c\u1eaft t\u1eeb \u0111i\u1ec3m m\u00e0 \u0111\u1ed1i s\u1ed1 th\u1ee9 nh\u1ea5t ch\u1ecdn cho \u0111\u1ebfn h\u1ebft ph\u1ea7n c\u00f2n l\u1ea1i c\u1ee7a chu\u1ed7i.<\/p>\n\n\n\n
V\u00ed d\u1ee5:<\/h3>\n\n\n\nvar res = str.slice(7);<\/code><\/pre>\n\n\n\nK\u1ebft qu\u1ea3: Banana, Kiwi<\/p>\n\n\n\n
\n\n\n\nho\u1eb7c l\u00e0 n\u00f3 s\u1ebd \u0111\u1ebfm t\u1eeb v\u1ecb tr\u00ed cu\u1ed1i.<\/p>\n\n\n\n
V\u00ed d\u1ee5:<\/h3>\n\n\n\nvar res = str.slice(-12);<\/code><\/pre>\n\n\n\nK\u1ebft qu\u1ea3: Banana, Kiwi<\/p>\n\n\n\n
\u0110\u1ed1i s\u1ed1 v\u1ecb tr\u00ed \u00e2m s\u1ebd kh\u00f4ng l\u00e0m vi\u1ec7c tr\u00ean Internet Explprer 8 v\u00e0 c\u00e1c phi\u00ean b\u1ea3n s\u1edbm h\u01a1n c\u1ee7a tr\u00ecnh duy\u1ec7t n\u00e0y.<\/p>\n\n\n\n
\n\n\n\n<\/span>Ph\u01b0\u01a1ng th\u1ee9c substring()<\/span><\/h2>\n\n\n\nsubstring()<\/code> <\/strong>t\u01b0\u01a1ng t\u1ef1 slice()<\/code>.<\/p>\n\n\n\nS\u1ef1 kh\u00e1c bi\u1ec7t l\u00e0 substring()<\/code> kh\u00f4ng ch\u1ea5p nh\u1eadn ch\u1ec9 s\u1ed1 \u00e2m.<\/p>\n\n\n\nV\u00ed d\u1ee5:<\/h3>\n\n\n\nvar str = \"Apple, Banana, Kiwi\";\nvar res = str.substring(7,13);<\/code><\/pre>\n\n\n\nK\u1ebft qu\u1ea3 l\u00e0: Banana<\/p>\n\n\n\n
N\u1ebfu b\u1ea1n b\u1ecf qua \u0111\u1ed1i s\u1ed1 th\u1ee9 hai, substring() s\u1ebd c\u1eaft t\u1eeb v\u1ecb tr\u00ed \u0111\u01b0\u1ee3c ch\u1ecdn cho \u0111\u1ebfn h\u1ebft chu\u1ed7i.<\/p>\n\n\n\n
\n\n\n\n<\/span>Ph\u01b0\u01a1ng th\u1ee9c substr()<\/span><\/h2>\n\n\n\nsubstr()<\/code> t\u01b0\u01a1ng t\u1ef1 slice()<\/code>.<\/p>\n\n\n\nS\u1ef1 kh\u00e1c bi\u1ec7t l\u00e0 \u0111\u1ed1i s\u1ed1 th\u1ee9 hai ch\u1ec9 \u0111\u1ecbnh chi\u1ec1u d\u00e0i c\u1ee7a chu\u1ed7i tr\u00edch xu\u1ea5t.<\/p>\n\n\n\n
V\u00ed d\u1ee5:<\/h3>\n\n\n\nvar str = \"Apple, Banana, Kiwi\";\nvar res = str.substr(7,6);<\/code><\/pre>\n\n\n\nK\u1ebft qu\u1ea3 s\u1ebd l\u00e0 : Banana<\/p>\n\n\n\n
N\u1ebfu \u0111\u1ed1i s\u1ed1 \u0111\u1ea7u l\u00e0 s\u1ed1 \u00e2m, v\u1ecb tr\u00ed s\u1ebd \u0111\u01b0\u1ee3c \u0111\u1ebfm t\u1eeb v\u1ecb tr\u00ed cu\u1ed1i c\u1ee7a chu\u1ed7i.<\/p>\n\n\n\n
\u0110\u1ed1i s\u1ed1 th\u1ee9 hai kh\u00f4ng th\u1ec3 l\u00e0 s\u1ed1 \u00e2m, b\u1edfi v\u00ec n\u00f3 \u0111\u1ecbnh ngh\u0129a chi\u1ec1u d\u00e0i chu\u1ed7i.<\/p>\n\n\n\n
N\u1ebfu b\u1ea1n b\u1ecf qua \u0111\u1ed1i s\u1ed1 th\u1ee9 hai, substr() s\u1ebd c\u1eaft t\u1eeb v\u1ecb tr\u00ed \u0111\u01b0\u1ee3c ch\u1ecdn cho \u0111\u1ebfn h\u1ebft ph\u1ea7n c\u00f2n l\u1ea1i c\u1ee7a chu\u1ed7i (gi\u1ed1ng c\u00e1c ph\u01b0\u01a1ng th\u1ee9c kia).<\/p>\n\n\n\n
\n\n\n\n<\/span>Thay th\u1ebf n\u1ed9i dung chu\u1ed7i<\/span><\/h2>\n\n\n\nPh\u01b0\u01a1ng th\u1ee9c replace()<\/code>\u00a0<\/strong>thay th\u1ebf gi\u00e1 tr\u1ecb ch\u1ec9 \u0111\u1ecbnh v\u1edbi gi\u00e1 tr\u1ecb kh\u00e1c trong m\u1ed9t chu\u1ed7i.<\/p>\n\n\n\nV\u00ed d\u1ee5:<\/h3>\n\n\n\nstr = \"Gh\u00e9 th\u0103m W3School \u0111\u1ec3 h\u1ecdc web!\";\nvar n = str.replace(\"W3School\",\"Ki\u1ebfn c\u00e0ng\");<\/code><\/pre>\n\n\n\nK\u1ebft qu\u1ea3: Gh\u00e9 th\u0103m Ki\u1ebfn c\u00e0ng \u0111\u1ec3 h\u1ecdc web!<\/p>\n\n\n\n
Ph\u01b0\u01a1ng th\u1ee9c replace() c\u00f3 thu\u1eadt to\u00e1n t\u00ecm ki\u1ebfm b\u00ean trong n\u00f3.<\/p>\n\n\n\n
Theo m\u1eb7c \u0111\u1ecbnh, h\u00e0m replace() ch\u1ec9 thay th\u1ebf gi\u00e1 tr\u1ecb tr\u00f9ng kh\u1edbp \u0111\u1ea7u ti\u00ean. \u0110\u1ec3 thay th\u1ebf t\u1ea5t c\u1ea3 c\u00e1c gi\u00e1 tr\u1ecb tr\u00f9ng kh\u1edbp, s\u1eed d\u00f9ng bi\u1ec3u th\u1ee9c th\u00f4ng th\u01b0\u1eddng v\u1edbi c\u1edd g (cho to\u00e0n b\u1ed9 gi\u00e1 tr\u1ecb tr\u00f9ng kh\u1edbp – global match).<\/p>\n\n\n\n
V\u00ed d\u1ee5:<\/h3>\n\n\n\nstr = \"Gh\u00e9 th\u0103m W3School \u0111\u1ec3 h\u1ecdc web!\";\nvar n = str.replace(\/W3School\/g,\"Ki\u1ebfn c\u00e0ng\");<\/code><\/pre>\n\n\n\nPh\u01b0\u01a1ng th\u1ee9c replace() kh\u00f4ng thay \u0111\u1ed5i chu\u1ed7i n\u00f3 g\u1ecdi \u0111\u1ebfn. N\u00f3 tr\u1ea3 v\u1ec1 m\u1ed9t chu\u1ed7i m\u1edbi.<\/p>\n\n\n\n
\n\n\n\n<\/span>Chuy\u1ec3n \u0111\u1ed5i th\u00e0nh ch\u1eef vi\u1ebft hoa ho\u1eb7c ch\u1eef vi\u1ebft th\u01b0\u1eddng<\/span><\/h2>\n\n\n\nM\u1ed9t chu\u1ed7i c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c chuy\u1ec3n th\u00e0nh ch\u1eef vi\u1ebft HOA v\u1edbi toUpperCase()<\/code>.<\/p>\n\n\n\nV\u00ed d\u1ee5:<\/h3>\n\n\n\nvar text1 = \"Ki\u1ebfn c\u00e0ng!\"; \/\/ Chu\u1ed7i\nvar text2 = text1.toUpperCase(); \/\/ Chu\u1ed7i n\u00e0y s\u1ebd \u0111\u01b0\u1ee3c chuy\u1ec3n h\u1ebft th\u00e0nh ch\u1eef vi\u1ebft HOA<\/code><\/pre>\n\n\n\nK\u1ebft qu\u1ea3: KI\u1ebeN C\u00c0NG<\/p>\n\n\n\n
M\u1ed9t chu\u1ed7i \u0111\u01b0\u1ee3c chuy\u1ec3n th\u00e0nh ch\u1eef th\u01b0\u1eddng v\u1edbi toLowerCase()<\/strong>.<\/p>\n\n\n\nV\u00ed d\u1ee5:<\/h3>\n\n\n\nvar text1 = \"Ki\u1ebfn c\u00e0ng\"; \/\/ Chu\u1ed7i\nvar text2 = text1.toLowerCase(); \/\/Chu\u1ed7i n\u00e0y s\u1ebd \u0111\u01b0\u1ee3c chuy\u1ec3n h\u1ebft th\u00e0nh ch\u1eef vi\u1ebft th\u01b0\u1eddng<\/code><\/pre>\n\n\n\nK\u1ebft qu\u1ea3: ki\u1ebfn c\u00e0ng<\/p>\n\n\n\n
\n\n\n\n<\/span>Ph\u01b0\u01a1ng th\u1ee9c concat()<\/span><\/h2>\n\n\n\nconcat()<\/code>\u00a0n\u1ed1i hai ho\u1eb7c nhi\u1ec1u chu\u1ed7i.<\/p>\n\n\n\nV\u00ed d\u1ee5:<\/h3>\n\n\n\nvar text1 = \"\u0110\u1ee9c Anh\";\nvar text2 = \"Plus\";\ntext3 = text1.concat(\" \",text2);<\/code><\/pre>\n\n\n\nK\u1ebft qu\u1ea3: \u0110\u1ee9c Anh Plus<\/p>\n\n\n\n
Ph\u01b0\u01a1ng th\u1ee9c concat() c\u00f3 th\u1ec3 s\u1eed d\u1ee5ng \u0111\u1ec3 thay th\u1ebf to\u00e1n t\u1eed c\u1ed9ng. Hai \u0111o\u1ea1n code n\u00e0y c\u00f3 \u00fd ngh\u0129a nh\u01b0 nhau.<\/p>\n\n\n\n
V\u00ed d\u1ee5:<\/h3>\n\n\n\nvar text = \"\u0110\u1ee9c Anh\" + \" \" + \"Plus\";\nvar text = \"\u0110\u1ee9c Anh\".concat(\" \",\"Plus\");<\/code><\/pre>\n\n\n\nT\u1ea5t c\u1ea3 ph\u01b0\u01a1ng th\u1ee9c string \u0111\u1ec1u tr\u1ea3 v\u1ec1 m\u1ed9t chu\u1ed7i m\u1edbi. Ch\u00fang kh\u00f4ng thay \u0111\u1ed5i chu\u1ed7i g\u1ed1c.<\/p>\n\n\n\n
N\u00f3i c\u00e1ch kh\u00e1c: Chu\u1ed7i l\u00e0 b\u1ea5t bi\u1ebfn, kh\u00f4ng th\u1ec3 thay \u0111\u1ed5i, ch\u1ec9 b\u1ecb thay th\u1ebf.<\/p>\n\n\n\n
\n\n\n\n<\/span>Tr\u00edch xu\u1ea5t k\u00fd t\u1ef1 trong chu\u1ed7i<\/span><\/h2>\n\n\n\nC\u00f3 hai ph\u01b0\u01a1ng th\u1ee9c an to\u00e0n \u0111\u1ec3 tr\u00edch xu\u1ea5t k\u00fd t\u1ef1 trong chu\u1ed7i:<\/p>\n\n\n\n
- charAt(v\u1ecb tr\u00ed)<\/li>
- charCodeAt(v\u1ecb tr\u00ed)<\/li><\/ul>\n\n\n\n
\n\n\n\n<\/span>Ph\u01b0\u01a1ng th\u1ee9c charAt()<\/span><\/h2>\n\n\n\nPh\u01b0\u01a1ng th\u1ee9c charAt()<\/code>\u00a0tr\u1ea3 v\u1ec1 k\u00fd t\u1ef1 t\u1ea1i v\u1ecb tr\u00ed ch\u1ec9 \u0111\u1ecbnh trong chu\u1ed7i.<\/p>\n\n\n\nV\u00ed d\u1ee5:<\/h3>\n\n\n\nvar str = \"Ki\u1ebfn c\u00e0ng\";\nstr.charAt(0); \/\/ tr\u1ea3 v\u1ec1 k\u1ebft qu\u1ea3 K<\/code><\/pre>\n\n\n\n
\n\n\n\n<\/span>Ph\u01b0\u01a1ng th\u1ee9c charCodeAt()<\/span><\/h2>\n\n\n\nPh\u01b0\u01a1ng th\u1ee9c charCodeAt()<\/code>\u00a0tr\u1ea3 v\u1ec1 m\u00e3 unicode c\u1ee7a k\u00fd t\u1ef1 t\u1ea1i v\u1ecb tr\u00ed ch\u1ec9 \u0111\u1ecbnh trong m\u1ed9t chu\u1ed7i.<\/p>\n\n\n\nV\u00ed d\u1ee5:<\/h3>\n\n\n\nvar str = \"\u0110\u1ee9c Anh Plus\";\nstr.charCodeAt(0); \/\/ tr\u1ea3 v\u1ec1 k\u1ebft qu\u1ea3 272<\/code><\/pre>\n\n\n\n
\n\n\n\n<\/span>Truy c\u1eadp m\u1ed9t chu\u1ed7i nh\u01b0 l\u00e0 M\u1ea3ng l\u00e0 Kh\u00f4ng an to\u00e0n<\/span><\/h2>\n\n\n\nB\u1ea1n c\u00f3 th\u1ec3 th\u1ea5y \u0111o\u1ea1n code gi\u1ed1ng nh\u01b0 th\u1ebf n\u00e0y, truy c\u1eadp m\u1ed9t chu\u1ed7i nh\u01b0 l\u00e0 m\u1ea3ng:<\/p>\n\n\n\n
var str = \"Ki\u1ebfn c\u00e0ng\";\nstr[0]; \/\/ Tr\u1ea3 v\u1ec1 k\u1ebft qu\u1ea3 K<\/code><\/pre>\n\n\n\nC\u00e1ch th\u1ee9c n\u00e0y l\u00e0 kh\u00f4ng an to\u00e0n<\/strong> v\u00e0 kh\u00f4ng th\u1ec3 \u0111o\u00e1n tr\u01b0\u1edbc<\/strong>:<\/p>\n\n\n\n