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Question about priority of logical operators

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alert( null || 2 && 3 || 4 );

alert( null || 2 && 3 || 4 );

alert( null || 2 && 3 || 4 );

alert( null || 2 && 3 || 4 );

4 Answers
4

active

oldest

votes

0

&& operator precedence is higher than that of ||. Thus null || 2 && 3 || 4 expression is effectively the same as null || (2 && 3) || 4.

Let's evaluate the entire expression step by step:

1. 
   null is a falsy value, so check the next operand


2. 
   (2 && 3) results in 3 which is a truthy value, it stops here and returns 3

share|improve this answer

edited Mar 23 at 14:48

answered Mar 23 at 14:42

abadalyanabadalyan

845613

add a comment | 

1

Is there higher priority of && over || operator?

Yes. This is called operator precedence. You can find a table for JS operators at MDN.

Your expression is evaluated like

alert((null || (2 && 3)) || 4);

To get left-to-right evaluation, you will need to write

alert((null || 2) && 3 || 4 );

share|improve this answer

edited Mar 23 at 14:44

answered Mar 23 at 14:42

BergiBergi

387k64601928

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  It still logs 3 and even if the precedence of || and && were swapped it would still log 3.
  
  – Paulpro
  Mar 23 at 15:07
  

  
  
  
  

add a comment | 

1

The order of evaluation is

null || (2 && 3) || 4
null || 3 || 4
 3 || 4
 3

logical AND && has a higher operator precedence than logical OR ||.

console.log(null || 2 && 3 || 4); // 3

share|improve this answer

edited Mar 23 at 14:47

answered Mar 23 at 14:42

Nina ScholzNina Scholz

204k16117188

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Order of evaluation doesn't matter much here. It would log 3 no matter what order: (null||2)&&(3||4) or (null||2) && 3 || 4 all evaluate to 3
  
  – Paulpro
  Mar 23 at 15:09
  

  
  
  
  

add a comment | 

0

The || operator runs next operand if it returns falsy value.

The && operator runs next operand if it returns truthy value.

Otherwise stop going further.

So,

- null || // false, go further
- 2 && // true, go further
- 3 || // true, stop

Thus, finally returns 3.

Edit:

If you talk about priority of the operator, then you may look at the operator precedence. Where you can see && operator has precedence value with 6 and || operator has precedence value with 5. So, && operator has higher order.

share|improve this answer

edited Mar 23 at 18:18

answered Mar 23 at 14:37

Bhojendra RauniyarBhojendra Rauniyar

53.7k2284136

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Before the edit, there was no mention of operator precedence which is necessary to answer the question. After the edit, I don't think your explanation of precedence is good - it has nothing to do with reordering.
  
  – Bergi
  Mar 23 at 18:00
  

  
  
  
  

add a comment | 

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0

&& operator precedence is higher than that of ||. Thus null || 2 && 3 || 4 expression is effectively the same as null || (2 && 3) || 4.

Let's evaluate the entire expression step by step:

1. 
   null is a falsy value, so check the next operand


2. 
   (2 && 3) results in 3 which is a truthy value, it stops here and returns 3

share|improve this answer

edited Mar 23 at 14:48

answered Mar 23 at 14:42

abadalyanabadalyan

845613

add a comment | 

0

&& operator precedence is higher than that of ||. Thus null || 2 && 3 || 4 expression is effectively the same as null || (2 && 3) || 4.

Let's evaluate the entire expression step by step:

1. 
   null is a falsy value, so check the next operand


2. 
   (2 && 3) results in 3 which is a truthy value, it stops here and returns 3

share|improve this answer

edited Mar 23 at 14:48

answered Mar 23 at 14:42

abadalyanabadalyan

845613

add a comment | 

&& operator precedence is higher than that of ||. Thus null || 2 && 3 || 4 expression is effectively the same as null || (2 && 3) || 4.

Let's evaluate the entire expression step by step:

1. 
   null is a falsy value, so check the next operand


2. 
   (2 && 3) results in 3 which is a truthy value, it stops here and returns 3

share|improve this answer

edited Mar 23 at 14:48

answered Mar 23 at 14:42

abadalyanabadalyan

845613

share|improve this answer

edited Mar 23 at 14:48

answered Mar 23 at 14:42

abadalyanabadalyan

845613

answered Mar 23 at 14:42

abadalyanabadalyan

845613

answered Mar 23 at 14:42

abadalyanabadalyan

845613

1

Is there higher priority of && over || operator?

Yes. This is called operator precedence. You can find a table for JS operators at MDN.

Your expression is evaluated like

alert((null || (2 && 3)) || 4);

To get left-to-right evaluation, you will need to write

alert((null || 2) && 3 || 4 );

share|improve this answer

edited Mar 23 at 14:44

answered Mar 23 at 14:42

BergiBergi

387k64601928

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  It still logs 3 and even if the precedence of || and && were swapped it would still log 3.
  
  – Paulpro
  Mar 23 at 15:07
  

  
  
  
  

add a comment | 

1

Is there higher priority of && over || operator?

Yes. This is called operator precedence. You can find a table for JS operators at MDN.

Your expression is evaluated like

alert((null || (2 && 3)) || 4);

To get left-to-right evaluation, you will need to write

alert((null || 2) && 3 || 4 );

share|improve this answer

edited Mar 23 at 14:44

answered Mar 23 at 14:42

BergiBergi

387k64601928

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  It still logs 3 and even if the precedence of || and && were swapped it would still log 3.
  
  – Paulpro
  Mar 23 at 15:07
  

  
  
  
  

add a comment | 

Is there higher priority of && over || operator?

Yes. This is called operator precedence. You can find a table for JS operators at MDN.

Your expression is evaluated like

alert((null || (2 && 3)) || 4);

To get left-to-right evaluation, you will need to write

alert((null || 2) && 3 || 4 );

share|improve this answer

edited Mar 23 at 14:44

answered Mar 23 at 14:42

BergiBergi

387k64601928

alert((null || (2 && 3)) || 4);

alert((null || 2) && 3 || 4 );

share|improve this answer

edited Mar 23 at 14:44

answered Mar 23 at 14:42

BergiBergi

387k64601928

answered Mar 23 at 14:42

BergiBergi

387k64601928

answered Mar 23 at 14:42

BergiBergi

387k64601928

1

The order of evaluation is

null || (2 && 3) || 4
null || 3 || 4
 3 || 4
 3

logical AND && has a higher operator precedence than logical OR ||.

console.log(null || 2 && 3 || 4); // 3

share|improve this answer

edited Mar 23 at 14:47

answered Mar 23 at 14:42

Nina ScholzNina Scholz

204k16117188

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Order of evaluation doesn't matter much here. It would log 3 no matter what order: (null||2)&&(3||4) or (null||2) && 3 || 4 all evaluate to 3
  
  – Paulpro
  Mar 23 at 15:09
  

  
  
  
  

add a comment | 

1

The order of evaluation is

null || (2 && 3) || 4
null || 3 || 4
 3 || 4
 3

logical AND && has a higher operator precedence than logical OR ||.

console.log(null || 2 && 3 || 4); // 3

share|improve this answer

edited Mar 23 at 14:47

answered Mar 23 at 14:42

Nina ScholzNina Scholz

204k16117188

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Order of evaluation doesn't matter much here. It would log 3 no matter what order: (null||2)&&(3||4) or (null||2) && 3 || 4 all evaluate to 3
  
  – Paulpro
  Mar 23 at 15:09
  

  
  
  
  

add a comment | 

The order of evaluation is

null || (2 && 3) || 4
null || 3 || 4
 3 || 4
 3

logical AND && has a higher operator precedence than logical OR ||.

console.log(null || 2 && 3 || 4); // 3

share|improve this answer

edited Mar 23 at 14:47

answered Mar 23 at 14:42

Nina ScholzNina Scholz

204k16117188

null || (2 && 3) || 4
null || 3 || 4
 3 || 4
 3

console.log(null || 2 && 3 || 4); // 3

console.log(null || 2 && 3 || 4); // 3

console.log(null || 2 && 3 || 4); // 3

share|improve this answer

edited Mar 23 at 14:47

answered Mar 23 at 14:42

Nina ScholzNina Scholz

204k16117188

answered Mar 23 at 14:42

Nina ScholzNina Scholz

204k16117188

answered Mar 23 at 14:42

Nina ScholzNina Scholz

204k16117188

0

The || operator runs next operand if it returns falsy value.

The && operator runs next operand if it returns truthy value.

Otherwise stop going further.

So,

- null || // false, go further
- 2 && // true, go further
- 3 || // true, stop

Thus, finally returns 3.

Edit:

If you talk about priority of the operator, then you may look at the operator precedence. Where you can see && operator has precedence value with 6 and || operator has precedence value with 5. So, && operator has higher order.

share|improve this answer

edited Mar 23 at 18:18

answered Mar 23 at 14:37

Bhojendra RauniyarBhojendra Rauniyar

53.7k2284136

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Before the edit, there was no mention of operator precedence which is necessary to answer the question. After the edit, I don't think your explanation of precedence is good - it has nothing to do with reordering.
  
  – Bergi
  Mar 23 at 18:00
  

  
  
  
  

add a comment | 

0

The || operator runs next operand if it returns falsy value.

The && operator runs next operand if it returns truthy value.

Otherwise stop going further.

So,

- null || // false, go further
- 2 && // true, go further
- 3 || // true, stop

Thus, finally returns 3.

Edit:

If you talk about priority of the operator, then you may look at the operator precedence. Where you can see && operator has precedence value with 6 and || operator has precedence value with 5. So, && operator has higher order.

share|improve this answer

edited Mar 23 at 18:18

answered Mar 23 at 14:37

Bhojendra RauniyarBhojendra Rauniyar

53.7k2284136

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Before the edit, there was no mention of operator precedence which is necessary to answer the question. After the edit, I don't think your explanation of precedence is good - it has nothing to do with reordering.
  
  – Bergi
  Mar 23 at 18:00
  

  
  
  
  

add a comment | 

The || operator runs next operand if it returns falsy value.

The && operator runs next operand if it returns truthy value.

Otherwise stop going further.

So,

- null || // false, go further
- 2 && // true, go further
- 3 || // true, stop

Thus, finally returns 3.

Edit:

If you talk about priority of the operator, then you may look at the operator precedence. Where you can see && operator has precedence value with 6 and || operator has precedence value with 5. So, && operator has higher order.

share|improve this answer

edited Mar 23 at 18:18

answered Mar 23 at 14:37

Bhojendra RauniyarBhojendra Rauniyar

53.7k2284136

- null || // false, go further
- 2 && // true, go further
- 3 || // true, stop

share|improve this answer

edited Mar 23 at 18:18

answered Mar 23 at 14:37

Bhojendra RauniyarBhojendra Rauniyar

53.7k2284136

answered Mar 23 at 14:37

Bhojendra RauniyarBhojendra Rauniyar

53.7k2284136

answered Mar 23 at 14:37

Bhojendra RauniyarBhojendra Rauniyar

53.7k2284136