Hi guys, following the topic of string handling in JS, today I will continue to introduce methods commonly used when working with string data that devjs cannot ignore. Let’s start
11. String.prototype.split ()
As the name implies, split()
splits a string into an ordered list of substring, places the substring in an array and returns the array.
1 2 3 4 5 6 7 8 9 10 11 12 13 | <span class="token keyword">const</span> str <span class="token operator">=</span> <span class="token string">'The quick brown fox jumps over the lazy dog.'</span> <span class="token punctuation">;</span> <span class="token keyword">const</span> words <span class="token operator">=</span> str <span class="token punctuation">.</span> <span class="token function">split</span> <span class="token punctuation">(</span> <span class="token string">' '</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> console <span class="token punctuation">.</span> <span class="token function">log</span> <span class="token punctuation">(</span> words <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment">// > Array ["The", "quick", "brown", "fox", "jumps", "over", "the", "lazy", "dog."]</span> console <span class="token punctuation">.</span> <span class="token function">log</span> <span class="token punctuation">(</span> words <span class="token punctuation">[</span> <span class="token number">3</span> <span class="token punctuation">]</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment">// > "fox"</span> <span class="token keyword">const</span> chars <span class="token operator">=</span> str <span class="token punctuation">.</span> <span class="token function">split</span> <span class="token punctuation">(</span> <span class="token string">''</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> console <span class="token punctuation">.</span> <span class="token function">log</span> <span class="token punctuation">(</span> chars <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment">// > Array ["T", "h", "e", " ", "q", "u", "i", "c", "k", " ", "b", "r", "o", "w", "n", " ", "f", "o", "x", " ", "j", "u", "m", "p", "s", " ", "o", "v", "e", "r", " ", "t", "h", "e", " ", "l", "a", "z", "y", " ", "d", "o", "g", "."]</span> console <span class="token punctuation">.</span> <span class="token function">log</span> <span class="token punctuation">(</span> chars <span class="token punctuation">[</span> <span class="token number">8</span> <span class="token punctuation">]</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment">// > "k"</span> <span class="token keyword">const</span> strCopy <span class="token operator">=</span> str <span class="token punctuation">.</span> <span class="token function">split</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> console <span class="token punctuation">.</span> <span class="token function">log</span> <span class="token punctuation">(</span> strCopy <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment">// > Array ["The quick brown fox jumps over the lazy dog."]</span> |
Syntax
1 2 3 4 5 6 7 8 9 10 11 12 | str <span class="token punctuation">.</span> <span class="token function">split</span> <span class="token punctuation">(</span> <span class="token punctuation">[</span> separator <span class="token punctuation">[</span> <span class="token punctuation">,</span> limit <span class="token punctuation">]</span> <span class="token punctuation">]</span> <span class="token punctuation">)</span> <span class="token comment">/* separator: Mẫu mô tả vị trí mỗi lần phân tách sẽ xảy ra. Dấu phân tách có thể là một chuỗi đơn giản hoặc nó có thể là một biểu thức chính quy. + Trường hợp đơn giản nhất là khi dấu phân cách chỉ là một ký tự đơn lẻ, nó được sử dụng để chia một chuỗi phân tách + Nếu dấu phân tách chứa nhiều ký tự, toàn bộ chuỗi ký tự đó phải được tìm thấy để tách + Nếu dấu phân tách bị bỏ qua hoặc không xuất hiện trong str, mảng được trả về chứa một phần tử bao gồm toàn bộ chuỗi + Nếu dấu phân tách xuất hiện ở đầu (hoặc cuối) của chuỗi, nó vẫn có tác dụng phân tách. Kết quả là một chuỗi rỗng (tức là độ dài bằng 0), xuất hiện ở vị trí đầu tiên (hoặc cuối cùng) của mảng được trả về. + Nếu dấu phân tách là một chuỗi rỗng (""), str được chuyển đổi thành một mảng của mỗi "ký tự" UTF-16 của nó */</span> <span class="token comment">/* limit (không bắt buộc): Một số nguyên không âm xác định, giới hạn về số lượng chuỗi con được đưa vào mảng */</span> |
12. String.prototype.substring ()
The substring()
returns the part of the string between the beginning and the end of the string, or the end of the string
1 2 3 4 5 | <span class="token keyword">const</span> str <span class="token operator">=</span> <span class="token string">'Mozilla'</span> <span class="token punctuation">;</span> console <span class="token punctuation">.</span> <span class="token function">log</span> <span class="token punctuation">(</span> str <span class="token punctuation">.</span> <span class="token function">substring</span> <span class="token punctuation">(</span> <span class="token number">1</span> <span class="token punctuation">,</span> <span class="token number">3</span> <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment">// > "oz"</span> console <span class="token punctuation">.</span> <span class="token function">log</span> <span class="token punctuation">(</span> str <span class="token punctuation">.</span> <span class="token function">substring</span> <span class="token punctuation">(</span> <span class="token number">2</span> <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment">// > "zilla"</span> |
Syntax
1 2 3 4 5 | str <span class="token punctuation">.</span> <span class="token function">substring</span> <span class="token punctuation">(</span> indexStart <span class="token punctuation">[</span> <span class="token punctuation">,</span> indexEnd <span class="token punctuation">]</span> <span class="token punctuation">)</span> <span class="token comment">// indexStart: Chỉ mục của ký tự đầu tiên</span> <span class="token comment">// indexEnd: Chỉ mục của ký tự cuối cùng</span> |
13. String.prototype.toString ()
The toString()
returns a string representing the specified object
1 2 3 4 5 | <span class="token keyword">const</span> stringObj <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">String</span> <span class="token punctuation">(</span> <span class="token string">'foo'</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> console <span class="token punctuation">.</span> <span class="token function">log</span> <span class="token punctuation">(</span> stringObj <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment">// > String { "foo" }</span> console <span class="token punctuation">.</span> <span class="token function">log</span> <span class="token punctuation">(</span> stringObj <span class="token punctuation">.</span> <span class="token function">toString</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment">// > "foo"</span> |
Syntax
1 2 | str <span class="token punctuation">.</span> <span class="token function">toString</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> |
14. String.prototype.toLowerCase ()
The toLowerCase()
returns a string converted to lowercase
1 2 3 4 | <span class="token keyword">const</span> sentence <span class="token operator">=</span> <span class="token string">'The quick brown fox jumps over the lazy dog.'</span> <span class="token punctuation">;</span> console <span class="token punctuation">.</span> <span class="token function">log</span> <span class="token punctuation">(</span> sentence <span class="token punctuation">.</span> <span class="token function">toLowerCase</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment">// > "the quick brown fox jumps over the lazy dog."</span> |
Syntax
1 2 | str <span class="token punctuation">.</span> <span class="token function">toLowerCase</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> |
15. String.prototype.toUpperCase ()
The toUpperCase()
returns a toUpperCase()
string
1 2 3 4 | <span class="token keyword">const</span> sentence <span class="token operator">=</span> <span class="token string">'The quick brown fox jumps over the lazy dog.'</span> <span class="token punctuation">;</span> console <span class="token punctuation">.</span> <span class="token function">log</span> <span class="token punctuation">(</span> sentence <span class="token punctuation">.</span> <span class="token function">toUpperCase</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment">// > "THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG."</span> |
16. String.prototype.trim ()
The trim()
removes spaces from both ends of a string. Whitespace in this context is all space characters (spaces, tabs, nonbreaking spaces, etc.) and all line-ending characters (LF, CR, etc.).
1 2 3 4 | <span class="token keyword">const</span> greeting <span class="token operator">=</span> <span class="token string">' Hello world! '</span> <span class="token punctuation">;</span> console <span class="token punctuation">.</span> <span class="token function">log</span> <span class="token punctuation">(</span> greeting <span class="token punctuation">.</span> <span class="token function">trim</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment">// > "Hello world!"</span> |
Syntax
1 2 | str <span class="token punctuation">.</span> <span class="token function">trim</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> |
17. String.prototype.trimEnd ()
The trimEnd()
removes spaces at the end of the string
1 2 3 4 | <span class="token keyword">const</span> greeting <span class="token operator">=</span> <span class="token string">' Hello world! '</span> <span class="token punctuation">;</span> console <span class="token punctuation">.</span> <span class="token function">log</span> <span class="token punctuation">(</span> greeting <span class="token punctuation">.</span> <span class="token function">trimEnd</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment">// > " Hello world!"</span> |
Syntax
1 2 | str <span class="token punctuation">.</span> <span class="token function">trimEnd</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> |
18. String.prototype.trimStart ()
The trimStart()
removes spaces at the end of the string
1 2 3 4 | <span class="token keyword">const</span> greeting <span class="token operator">=</span> <span class="token string">' Hello world! '</span> <span class="token punctuation">;</span> console <span class="token punctuation">.</span> <span class="token function">log</span> <span class="token punctuation">(</span> greeting <span class="token punctuation">.</span> <span class="token function">trimStart</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment">// > "Hello world! "</span> |
Syntax
1 2 | str <span class="token punctuation">.</span> <span class="token function">trimStart</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> |
19. String.prototype.valueOf ()
The valueOf()
returns a primitive value of a string object
1 2 3 4 5 | <span class="token keyword">const</span> stringObj <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">String</span> <span class="token punctuation">(</span> <span class="token string">'foo'</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> console <span class="token punctuation">.</span> <span class="token function">log</span> <span class="token punctuation">(</span> stringObj <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment">// > String { "foo" }</span> console <span class="token punctuation">.</span> <span class="token function">log</span> <span class="token punctuation">(</span> stringObj <span class="token punctuation">.</span> <span class="token function">valueOf</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment">// > "foo"</span> |
Syntax
1 2 | str <span class="token punctuation">.</span> <span class="token function">valueOf</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> |
Conclude
Above I have introduced to you most of the common methods when manipulating String data, hoping to be useful for you in the working process.
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