Hello everyone , in the first article of the series ” Some cool tips” of ES6 “, I shared a few small tips and have received more or less attention from everyone. Today, I would like to continue with part 2 of this series. Please follow along!
1. Check 1 variable has the value NaN
JavaScript has one thing oddly, NaN is the only value NEVER by itself. So how do we check its true and false?
1 2 3 4 5 | <span class="token keyword">const</span> value <span class="token operator">=</span> <span class="token number">NaN</span> <span class="token punctuation">;</span> value <span class="token operator">===</span> <span class="token number">NaN</span> <span class="token punctuation">;</span> <span class="token comment">// false</span> |
Don’t worry, ES6 has introduced a new method for solving this problem, Object.is . Let’s see how it works!
1 2 3 4 5 6 | <span class="token keyword">const</span> divide <span class="token operator">=</span> <span class="token number">5</span> <span class="token operator">/</span> <span class="token string">"two"</span> <span class="token punctuation">;</span> <span class="token comment">//NaN</span> divide <span class="token operator">===</span> <span class="token number">NaN</span> <span class="token punctuation">;</span> Object <span class="token punctuation">.</span> <span class="token function">is</span> <span class="token punctuation">(</span> divide <span class="token punctuation">,</span> <span class="token number">NaN</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment">// true</span> |
2. Calculate with string data type
If suppose you get data returned including numbers and strings, but for some reason you … lazy to not want to waste the effort converting the string to number before performing the calculation, then apply Now “tips” below see stars
1 2 3 4 5 6 7 8 9 | <span class="token keyword">const</span> string <span class="token operator">=</span> <span class="token string">'100'</span> <span class="token punctuation">;</span> <span class="token keyword">const</span> number <span class="token operator">=</span> <span class="token number">5</span> <span class="token punctuation">;</span> <span class="token comment">// Nếu thực hiện tính tổng thông thường</span> console <span class="token punctuation">.</span> <span class="token function">log</span> <span class="token punctuation">(</span> string <span class="token operator">+</span> number <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment">// 1005</span> <span class="token comment">// Hack 1 chút với phương thức +string</span> console <span class="token punctuation">.</span> <span class="token function">log</span> <span class="token punctuation">(</span> <span class="token operator">+</span> string <span class="token operator">+</span> number <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment">// 105</span> |
3. Check for existence of subString in String
In ES5, to check for the existence of a string in a string, or an item in an array, we often use the indexOf syntax.
But since ES6 version, you can use the includes() to test if a string contains a substring or not. It determines if the string exists in another string or not, the result will be true or false .
1 2 3 4 5 6 7 8 | <span class="token keyword">const</span> company <span class="token operator">=</span> <span class="token string">'sun asterisk'</span> <span class="token punctuation">;</span> <span class="token comment">// ES5</span> company <span class="token punctuation">.</span> <span class="token function">indexOf</span> <span class="token punctuation">(</span> <span class="token string">'sun'</span> <span class="token punctuation">)</span> <span class="token operator">!==</span> <span class="token operator">-</span> <span class="token number">1</span> <span class="token punctuation">;</span> <span class="token comment">// true</span> <span class="token comment">// ES6</span> company <span class="token punctuation">.</span> <span class="token function">includes</span> <span class="token punctuation">(</span> <span class="token string">'sun'</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment">// true</span> |
or
1 2 3 4 | <span class="token keyword">const</span> company <span class="token operator">=</span> <span class="token punctuation">[</span> <span class="token string">'sun'</span> <span class="token punctuation">,</span> <span class="token string">'asterisk'</span> <span class="token punctuation">,</span> <span class="token string">'framgia'</span> <span class="token punctuation">]</span> <span class="token punctuation">;</span> company <span class="token punctuation">.</span> <span class="token function">includes</span> <span class="token punctuation">(</span> <span class="token string">'sun'</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment">// true</span> |
4. Remove Duplicates Array
In the previous part, I introduced a method to remove duplicate elements in an array, that is, using the syntax ... In addition, there is one more method of ES6 to do this.
1 2 3 4 5 6 7 | <span class="token keyword">const</span> arrray <span class="token operator">=</span> <span class="token punctuation">[</span> <span class="token number">1</span> <span class="token punctuation">,</span> <span class="token number">2</span> <span class="token punctuation">,</span> <span class="token number">2</span> <span class="token punctuation">,</span> <span class="token number">3</span> <span class="token punctuation">,</span> <span class="token number">3</span> <span class="token punctuation">,</span> <span class="token number">3</span> <span class="token punctuation">,</span> <span class="token number">4</span> <span class="token punctuation">,</span> <span class="token number">4</span> <span class="token punctuation">,</span> <span class="token number">4</span> <span class="token punctuation">,</span> <span class="token number">4</span> <span class="token punctuation">]</span> <span class="token punctuation">;</span> <span class="token keyword">const</span> removeDuplicate <span class="token operator">=</span> Array <span class="token punctuation">.</span> <span class="token function">from</span> <span class="token punctuation">(</span> <span class="token keyword">new</span> <span class="token class-name">Set</span> <span class="token punctuation">(</span> arrray <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> removeDuplicate <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token comment">// [1,2,3,4]</span> |
Above are some more tips in the series ” Some cool tips” of ES6 “. Hope to help you in work and study.
I would like to end part 2 here. Good bye and see you again!