Q:

How to plus to each other numbers from tags

I need to plus each number from tags.  but can't figureout how to do this, Javascript is new for me. 
html
<span class="number">1</span>
<span class="number">2</span>
<span class="number">3</span>
<span class="number">4</span>

javascript
var number = document.querySelectorAll('.number');

for ( var i = 0; i < number.length; i++ ) {

    var nums = number[i].textContent;
    var Result = //code to get 1+2+3+4
    console.log(result); // Result must be 10

}

A:

There are lots of ways to solve this problem.  Above in your code you are writing code in the loop.  which should not be.  
You want to add all the items So you can use following code
var result=0;
for ( var i = 0; i < numbers.length; i++ ) {
        result+= +numbers[i].textContent;
    }
    console.log(result);

or 
[].slice.call(document.querySelectorAll(".number")).reduce((x,y)=>{
    return ((+x.textContent)||x) + +y.textContent
})

Code is as follows

var numbers=document.querySelectorAll(".number");
var result=0;

for ( var i = 0; i < numbers.length; i++ ) {
    result+= +numbers[i].textContent;
}
console.log(result); 
<span class="number">1</span>
<span class="number">2</span>
<span class="number">3</span>
<span class="number">4</span>

or 

var result=[].slice.call(document.querySelectorAll(".number")).reduce((x,y)=>{
    return ((+x.textContent)||x) + +y.textContent
});
console.log(result);
<span class="number">1</span>
<span class="number">2</span>
<span class="number">3</span>
<span class="number">4</span>

