Javascript reduces an array of sums with undefined values

Question

I have this simple array with numbers:

var arr = [100,200,undefined,450,300];

I would like to use reduceto quickly sum the values ​​in this array, for example ...

var total = arr.reduce( function( s, v ){ return s += v } );

In returnI get NaN.

Is there any way to do reduceto sum values ​​in an array with undefined values? like a flag or something ... Thank you!

Answer 1

You can use the default value for falsy values ( undefined, null, 0, ''and a few more) with logical the OR|| , for example,

v || 0

, v truthy, , , .

var arr = [100, 200, undefined, 450, 300],
    total = arr.reduce(function (s, v) { return s + (v || 0); }, 0);

console.log(total);

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BTW,

s += v
   ^ 

, s . - s . , .

---

• , , , .

  • ,

    .filter(v => !isNaN(v))
    

  • .map(Number)
    

• , , , .

  function add(a, b) {
      return a + b;
  }
  

• Array#reduce

  initialValue ()

  , callback. , . reduce() - .

  result = array
      .filter(v => !isNaN(v))
      .map(Number)
      .reduce(add, 0);
  

Answer 2

.

, , , .

var arr = [100,200,undefined,450,300,'string'];

var total = arr
  .filter(function(x) { return typeof(x) === 'number'}) // remove any non numbers
  .reduce(function( s, v ){ return s + Number(v) }, 0);
  
console.log(
  total
)

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Answer 3

Just a Trojan should

var arr = [100, 200, undefined, 450, 300];

var total = arr.reduce(function(s, v) {
return v ? s += v : s += 0
});

console.log(total);

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Answer 4

Try with filter():

var arr = [100,200,undefined,450,300];

var total = arr.filter(i=>i != undefined).reduce( function( s, v ){ 
    return s += v;
  }, 0);
  
console.log(total)

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