I have a code in reactjs which sends datas entered in a form using axios. And it works fine. You have below a code with the same architecture as mine.  export default class FormPage extends Component {      constructor(props) {       super(props);       this.state = initialState;       this.handleSubmit = this.handleSubmit.bind(this);       this.handleChange = this.handleChange.bind(this);      }       showMessage = (bool) =&gt; {       setTimeout(() =&gt; {        this.setState({         showMessage: true        });       }, 2000);      if (this.state.Showing) return;       this.setState({ Show: true, Showing: true });      setTimeout(() =&gt; {       this.setState({ Show: false, Showing: false });       }, 2000);      }       showMessageFalse = (bool) =&gt; {       this.setState({        showMessage: false        });       this.setState(initialState);      }       handleChange(event) {       const InputValue = event.target.value;       const stateField = event.target.name;       this.setState({         [stateField]: InputValue,       });       console.log(this.state);      }       async handleSubmit(event) {       this.setState({ loading: true });        setTimeout(() =&gt; {        this.setState({ loading: false });       }, 2000);       event.preventDefault();      const {        name_contact='',      } = this.state;       await axios.post(       ' MY_endpoint API',       {         name: `${name_contact}`);       }    render() {      const { loading } = this.state;      return (       &lt;div&gt;          &lt;ExpansionPanel title="Contacts" expandedTitle="Contacts" titleIcon="done_all" &gt;&lt;div&gt;           &lt;Container&gt;             &lt;div id="normal"&gt;&lt;label id='title2'&gt;Detail du contact&lt;/label&gt;&lt;/div&gt;&lt;br/&gt;               &lt;Row align="center"&gt;                 &lt;Col id= "color" sm={3}&gt; &lt;label&gt; Name: &lt;/label&gt;&lt;/Col&gt; &lt;Col id= "color" sm={3}&gt;&lt;Input placeholder="Nom complet" type="string" name="name_contact" value={this.state.name_contact} onChange={this.handleChange}/&gt;&lt;br /&gt; &lt;/Col&gt;               &lt;/Row&gt;           &lt;/Container&gt;           &lt;/div&gt;         &lt;/ExpansionPanel&gt;        &lt;form onSubmit={this.handleSubmit}&gt;       &lt;br /&gt;&lt;br /&gt;&lt;div id="deb"&gt;&lt;Button type="submit" value="Show" onClick={this.showMessageFalse.bind(null, true)} &gt; Update &lt;/Button&gt;&lt;/div&gt;       &lt;/form&gt;     &lt;/div&gt;     );   } }   But on my real code, I have a lot of datas to send because i have a lot of field. I would like to know if it was possible to send with this architecture, only the fields where a variable is in.  event.preventDefault();  const {    name_contact='',  } = this.state;   await axios.post(   ' MY_endpoint API',   {     name: `${name_contact}`);   }   i want for example, if my name_contact is not filled and I click on "Update", it does not send the name_contact field, but if it is filled, it sends it.  If it’s possible to do something like that, what am I supposed to use? Thanks
How do I remove all attributes which are undefined or null in a JavaScript object?  (Question is similar to  for Arrays)
My Developer Account cannot be activated because I used a relative's credit card First part :  I want to prove the following De Morgan's law :  ref.(dfeuer)  $A\setminus (B \cap C) = (A\setminus B) \cup (A\setminus C) $    Second part:  Prove that $(A\setminus B) \cup (A\setminus C) = A\setminus (B \cap C) $    Proof:  Let $y\in (A\setminus B) \cup (A\setminus C)$     $(A\setminus B) \cup (A\setminus C) = (y \in A\;  \land y \not\in  B\;) \vee (y \in A\; \land y \not\in C\;)$      $\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;= y \in A\ \land (  y \not\in B\; \vee \; y \not\in C ) $      $\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;= y \in A \land  (\lnot ( y\in B) \lor \lnot( y\in C) )$   According to De-Morgan's theorem :  $\lnot( B \land C) \Longleftrightarrow (\lnot B \lor \lnot C)$ thus     $y \in A \land (\lnot ( y\in B) \lor \lnot( y\in C) ) = y \in A \land y \not\in (B \land C)$   We can conclude that  $(A\setminus B) \cup (A\setminus C) = A\setminus (B \cap C)$ biblatex - issue number of journal in date Padding is missing under the &quot;Communities&quot; border line, and the list is also showing &quot;Communities (0)&quot; (maybe the reason is due to caching as it shows 0 Communities):  Generally, padding is present: Is a function defined at a single point continuous? Is a function defined at a single point continuous?  For example $f:\{0\}\to\{0\}$ defined by $f(x)=\sqrt{x}+\sqrt{-x}$ is a sum of two continuous functions and is therefore continuous, however for $f$ to be continuous, it has to have the limit $\lim\limits_{x_0\to x}f(x_0)=f(x)$ but it dosen't seem to have that limit. How to peel hard boiled eggs easily? This is one of the most annoying duties in the kitchen, for me.  What are yours tips and tricks to peel hard boiled eggs easily? Find expected value of $\frac{1}{1+\xi}$ Find expected value of $\frac{1}{1+\xi}$ if $\xi$ has Poisson distribution.  My try:  $$E\left[ \frac{1}{1+\xi}\right]=\sum_{k=0}^{\infty}{x}_{k}{p}_{k}=\sum_{k=0}^{\infty}\frac{1}{k+1}\frac{\lambda^ke^{-\lambda}}{k!}$$  Is it right? Why is my voice command missing from the ok glass menu in XE16? I have a friend who is playing with me on a server we've created. Unfortunately, he is on a  Mac whereas I am on a Windows machine. I told him that I should be able to compile and send a .minecraft folder to him so that we can both play. Unfortunately, he can't find his .minecraft folder where it is supposed to be. Is it hidden and how can I unhide it? When will data.SE get updated data? Big O, how do you calculate/approximate it? Most people with a degree in CS will certainly know what . It helps us to measure how well an algorithm scales.   But I'm curious, how do you calculate or approximate the complexity of your algorithms? How to decide whether missing values are MAR, MCAR, or MNAR I have a large proteomics dataset. In the rows I have the proteins , and in the rows I have the samples.The dataset contains a lot of missing values.  I would like to know I can find out whether missing values are MAR, MCAR, or MNAR, and how I can decide the best imputation technique. Kind regards. How do I remove all specific characters at the end of a string in PHP? Consider repeated measures ANOVA (RM-ANOVA) with one within-subject factor A and several measurements per subject for each level of A.  It is closely related to two-way ANOVA with two factors: A and subject. They use identical decomposition of the sum of squares into four parts: A, subject, A⋅subject, and residual. However, two-way ANOVA tests the effect of A by comparing SS of A with the residual SS, while RM-ANOVA tests the effect of A by comparing SS of A with the A$\cdot$subject interaction SS.   Why the difference?    Does this difference automatically follow from the repeated-measures structure of the data, or is it some convention?  Does this difference between two-way ANOVA and RM-ANOVA correspond to testing two different nulls? If so, what exactly are they and why would we use different nulls in these two cases? Two-way ANOVA's test can be understood as an F-test between two nested models: the full model, and the model without A. Can RM-ANOVA be understood in a similar way?   (If there is only one measurement per subject for each level of A, then the distinction sort of disappears because A$\cdot$subject and residual variation cannot be disentangled: )    Demonstration  I will use toy data d2 generated in . The same webpage shows correct syntax for RM-ANOVA.  # Discarding between-subject factors and leaving only one within-subject factor d = d2[d2$Xb1=='CG' &amp; d2$Xb2 == 'f', c(1,4,6)]   (See reproducible version .) Data look like that:       id Xw1     Y 1    s1   A  28.6 2    s1   A  96.6 3    s1   A  64.8 4    s1   B 107.5 5    s1   B  77.3 6    s1   B 120.9 7    s1   C 141.2 8    s1   C 124.1 9    s1   C  88.0 10   s2   A  86.7 ...   Here is two-way ANOVA: summary(aov(Y ~ Xw1*id, d))               Df Sum Sq Mean Sq F value   Pr(&gt;F)     Xw1           2  95274   47637  16.789 3.73e-07 *** id           19  31359    1650   0.582    0.913     Xw1:id       38  71151    1872   0.660    0.929     Residuals   120 340490    2837                    Here is RM-ANOVA: summary(aov(Y ~ Xw1 + Error(id/Xw1), d))  Error: id           Df Sum Sq Mean Sq F value Pr(&gt;F) Residuals 19  31359    1650                 Error: id:Xw1           Df Sum Sq Mean Sq F value   Pr(&gt;F)     Xw1        2  95274   47637   25.44 9.73e-08 *** Residuals 38  71151    1872                       Error: Within            Df Sum Sq Mean Sq F value Pr(&gt;F) Residuals 120 340490    2837               Note the identical SS decomposition, but two-way ANOVA tests Xw1 against the residual, while RM-ANOVA tests Xw1 against the Xw1:id interaction.  Why?  This question is related to . If we try using Error(id) instead of Error(id/Xw1) in the example above, then Xw1 will get tested against Xw1:id interaction lumped together with the residual variation.  (The same issue arises in factorial RM-ANOVA with multiple within-subject factors, where each factor or interaction is tested against its own "error term" aka "error stratum". These error strata are always given by the corresponding interaction with the block/plot/subject variable id.) “Screen overlay detected” dialog? Turned off everything, doesn't work I started receiving the “Screen overlay detected” dialog when trying to change apps settings.  Tried to turn off all "draw over other apps" as it says here - , first without system and then with, but it still doesn't work.  Then, I restored apps to original settings and it just made a bigger mess, dialog continue appearing. Any way to go back to previous settings???  Thanks! How do you prevent an ENTER key press from submitting a form in a web-based application? Derivation of binomial coefficient in binomial theorem. How was the binomial coefficient of the binomial theorem derived?  $$\frac{n!}{k!(n-k)!}$$ Google Voice Recognition on iOS Windows installer for Ubuntu 14.04 LTS onwards I often find myself in a situation where I am facing multiple compilation/linker errors in a C++ project due to some bad design decisions (made by someone else :) ) which lead to circular dependencies between C++ classes in different header files (can happen also in the same file). But fortunately(?) this doesn't happen often enough for me to remember the solution to this problem for the next time it happens again.  So for the purposes of easy recall in the future I am going to post a representative problem and a solution along with it. Better solutions are of-course welcome.     A.h  class B; class A {     int _val;     B *_b; public:      A(int val)         :_val(val)     {     }      void SetB(B *b)     {         _b = b;         _b-&gt;Print(); // COMPILER ERROR: C2027: use of undefined type 'B'     }      void Print()     {         cout&lt;&lt;"Type:A val="&lt;&lt;_val&lt;&lt;endl;     } };       B.h  #include "A.h" class B {     double _val;     A* _a; public:      B(double val)         :_val(val)     {     }      void SetA(A *a)     {         _a = a;         _a-&gt;Print();     }      void Print()     {         cout&lt;&lt;"Type:B val="&lt;&lt;_val&lt;&lt;endl;     } };       main.cpp  #include "B.h" #include &lt;iostream&gt;  int main(int argc, char* argv[]) {     A a(10);     B b(3.14);     a.Print();     a.SetB(&amp;b);     b.Print();     b.SetA(&amp;a);     return 0; }