Can a predicate be an object in JavaScript?

-1

Can a predicate be an object in JavaScript (as in C++)?

For example, is it possible to find the index of an element in an array (with arr.findIndex(pred)) with a predicate like this?

 class Predicate
 
 constructor()
 
 this.sum = 0;
 

 evaluate(elem)
 
 this.sum += elem;
 return sum > 25;
 
 

 const pred = new Predicate();

 const index = arr.findIndex(pred);

EDIT1: If no, what is the easiest way to find the index of an element that makes the sum of it and all the previous elements exceed 25?

edited Nov 15 '18 at 13:19

asked Nov 15 '18 at 13:11

Alexey Starinsky

677111

1

Can a predicate be an object in JavaScript? -> NO

– Anand Undavia
Nov 15 '18 at 13:14

add a comment |

-1

Can a predicate be an object in JavaScript (as in C++)?

For example, is it possible to find the index of an element in an array (with arr.findIndex(pred)) with a predicate like this?

 class Predicate
 
 constructor()
 
 this.sum = 0;
 

 evaluate(elem)
 
 this.sum += elem;
 return sum > 25;
 
 

 const pred = new Predicate();

 const index = arr.findIndex(pred);

EDIT1: If no, what is the easiest way to find the index of an element that makes the sum of it and all the previous elements exceed 25?

edited Nov 15 '18 at 13:19

asked Nov 15 '18 at 13:11

Alexey Starinsky

677111

1

Can a predicate be an object in JavaScript? -> NO

– Anand Undavia
Nov 15 '18 at 13:14

add a comment |

-1

Can a predicate be an object in JavaScript (as in C++)?

For example, is it possible to find the index of an element in an array (with arr.findIndex(pred)) with a predicate like this?

 class Predicate
 
 constructor()
 
 this.sum = 0;
 

 evaluate(elem)
 
 this.sum += elem;
 return sum > 25;
 
 

 const pred = new Predicate();

 const index = arr.findIndex(pred);

EDIT1: If no, what is the easiest way to find the index of an element that makes the sum of it and all the previous elements exceed 25?

edited Nov 15 '18 at 13:19

asked Nov 15 '18 at 13:11

Alexey Starinsky

677111

Can a predicate be an object in JavaScript (as in C++)?

For example, is it possible to find the index of an element in an array (with arr.findIndex(pred)) with a predicate like this?

 class Predicate
 
 constructor()
 
 this.sum = 0;
 

 evaluate(elem)
 
 this.sum += elem;
 return sum > 25;
 
 

 const pred = new Predicate();

 const index = arr.findIndex(pred);

EDIT1: If no, what is the easiest way to find the index of an element that makes the sum of it and all the previous elements exceed 25?

javascript

edited Nov 15 '18 at 13:19

asked Nov 15 '18 at 13:11

Alexey Starinsky

677111

edited Nov 15 '18 at 13:19

asked Nov 15 '18 at 13:11

Alexey Starinsky

677111

edited Nov 15 '18 at 13:19

asked Nov 15 '18 at 13:11

Alexey Starinsky

677111

asked Nov 15 '18 at 13:11

Alexey Starinsky

677111

asked Nov 15 '18 at 13:11

Alexey Starinsky

677111

1

Can a predicate be an object in JavaScript? -> NO

– Anand Undavia
Nov 15 '18 at 13:14

add a comment |

1

Can a predicate be an object in JavaScript? -> NO

– Anand Undavia
Nov 15 '18 at 13:14

Can a predicate be an object in JavaScript? -> NO

– Anand Undavia
Nov 15 '18 at 13:14

add a comment |

3 Answers
3

active

oldest

votes

It should be a callback, this the function definition

arr.findIndex(callback(element[, index[, array]])[, thisArg])

You can provide your Predicate objects evaluate method. Like this

const index = arr.findIndex(pred.evaluate,pred);// pass pred as thisArg

edited Nov 15 '18 at 13:59

answered Nov 15 '18 at 13:16

Abhi

35310

1

You need to either bind the method or pass the instance as a thisArg

– Yury Tarabanko
Nov 15 '18 at 13:19

findIndex is being called on arr (Array), method is bound to the array. It runs perfectly fine.

– Abhi
Nov 15 '18 at 13:31

Well, no jsfiddle.net/4ga3sLy9

– Yury Tarabanko
Nov 15 '18 at 13:37

my bad, i removed his logic and just tested the callback. Edited answer.Thank you for pointing out! jsfiddle.net/4ga3sLy9/3

– Abhi
Nov 15 '18 at 13:59

add a comment |

Predicate has to be a function. MDN. But you could always create a function that returns another function.

const runningSum = (sum, current = 0) => value => (current += value) > sum

const index = [1, 2, 3, 4, 5, 6, 7, 8, 9].findIndex(runningSum(25))

console.log(index)

answered Nov 15 '18 at 13:23

Yury Tarabanko

30.9k64668

add a comment |

There is no such thing as an evaluate method (that would get invoked when an object gets called like a function) in JavaScript. However, functions themselves are objects and you could even create them with class syntax. It's not very useful though, in JS you would just write a closure to create a function with instance-specific values:

function predicate(max) 
 var sum = 0;
 return function(elem) 
 sum += elem;
 return sum > max;
 ;


const pred = predicate(25);

const index = arr.findIndex(pred);

answered Nov 15 '18 at 13:25

Bergi

377k63574903

add a comment |

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3 Answers
3

active

oldest

votes

3 Answers
3

active

oldest

votes

It should be a callback, this the function definition

arr.findIndex(callback(element[, index[, array]])[, thisArg])

You can provide your Predicate objects evaluate method. Like this

const index = arr.findIndex(pred.evaluate,pred);// pass pred as thisArg

edited Nov 15 '18 at 13:59

answered Nov 15 '18 at 13:16

Abhi

35310

1

You need to either bind the method or pass the instance as a thisArg

– Yury Tarabanko
Nov 15 '18 at 13:19

findIndex is being called on arr (Array), method is bound to the array. It runs perfectly fine.

– Abhi
Nov 15 '18 at 13:31

Well, no jsfiddle.net/4ga3sLy9

– Yury Tarabanko
Nov 15 '18 at 13:37

my bad, i removed his logic and just tested the callback. Edited answer.Thank you for pointing out! jsfiddle.net/4ga3sLy9/3

– Abhi
Nov 15 '18 at 13:59

add a comment |

It should be a callback, this the function definition

arr.findIndex(callback(element[, index[, array]])[, thisArg])

You can provide your Predicate objects evaluate method. Like this

const index = arr.findIndex(pred.evaluate,pred);// pass pred as thisArg

edited Nov 15 '18 at 13:59

answered Nov 15 '18 at 13:16

Abhi

35310

1

You need to either bind the method or pass the instance as a thisArg

– Yury Tarabanko
Nov 15 '18 at 13:19

findIndex is being called on arr (Array), method is bound to the array. It runs perfectly fine.

– Abhi
Nov 15 '18 at 13:31

Well, no jsfiddle.net/4ga3sLy9

– Yury Tarabanko
Nov 15 '18 at 13:37

my bad, i removed his logic and just tested the callback. Edited answer.Thank you for pointing out! jsfiddle.net/4ga3sLy9/3

– Abhi
Nov 15 '18 at 13:59

add a comment |

It should be a callback, this the function definition

arr.findIndex(callback(element[, index[, array]])[, thisArg])

You can provide your Predicate objects evaluate method. Like this

const index = arr.findIndex(pred.evaluate,pred);// pass pred as thisArg

edited Nov 15 '18 at 13:59

answered Nov 15 '18 at 13:16

Abhi

35310

It should be a callback, this the function definition

arr.findIndex(callback(element[, index[, array]])[, thisArg])

You can provide your Predicate objects evaluate method. Like this

const index = arr.findIndex(pred.evaluate,pred);// pass pred as thisArg

edited Nov 15 '18 at 13:59

answered Nov 15 '18 at 13:16

Abhi

35310

edited Nov 15 '18 at 13:59

answered Nov 15 '18 at 13:16

Abhi

35310

answered Nov 15 '18 at 13:16

Abhi

35310

answered Nov 15 '18 at 13:16

Abhi

35310

1

You need to either bind the method or pass the instance as a thisArg

– Yury Tarabanko
Nov 15 '18 at 13:19

findIndex is being called on arr (Array), method is bound to the array. It runs perfectly fine.

– Abhi
Nov 15 '18 at 13:31

Well, no jsfiddle.net/4ga3sLy9

– Yury Tarabanko
Nov 15 '18 at 13:37

my bad, i removed his logic and just tested the callback. Edited answer.Thank you for pointing out! jsfiddle.net/4ga3sLy9/3

– Abhi
Nov 15 '18 at 13:59

add a comment |

1

You need to either bind the method or pass the instance as a thisArg

– Yury Tarabanko
Nov 15 '18 at 13:19

findIndex is being called on arr (Array), method is bound to the array. It runs perfectly fine.

– Abhi
Nov 15 '18 at 13:31

Well, no jsfiddle.net/4ga3sLy9

– Yury Tarabanko
Nov 15 '18 at 13:37

my bad, i removed his logic and just tested the callback. Edited answer.Thank you for pointing out! jsfiddle.net/4ga3sLy9/3

– Abhi
Nov 15 '18 at 13:59

You need to either bind the method or pass the instance as a thisArg

– Yury Tarabanko
Nov 15 '18 at 13:19

findIndex is being called on arr (Array), method is bound to the array. It runs perfectly fine.

– Abhi
Nov 15 '18 at 13:31

Well, no jsfiddle.net/4ga3sLy9

– Yury Tarabanko
Nov 15 '18 at 13:37

my bad, i removed his logic and just tested the callback. Edited answer.Thank you for pointing out! jsfiddle.net/4ga3sLy9/3

– Abhi
Nov 15 '18 at 13:59

add a comment |

Predicate has to be a function. MDN. But you could always create a function that returns another function.

const runningSum = (sum, current = 0) => value => (current += value) > sum

const index = [1, 2, 3, 4, 5, 6, 7, 8, 9].findIndex(runningSum(25))

console.log(index)

answered Nov 15 '18 at 13:23

Yury Tarabanko

30.9k64668

add a comment |

Predicate has to be a function. MDN. But you could always create a function that returns another function.

const runningSum = (sum, current = 0) => value => (current += value) > sum

const index = [1, 2, 3, 4, 5, 6, 7, 8, 9].findIndex(runningSum(25))

console.log(index)

answered Nov 15 '18 at 13:23

Yury Tarabanko

30.9k64668

add a comment |

Predicate has to be a function. MDN. But you could always create a function that returns another function.

const runningSum = (sum, current = 0) => value => (current += value) > sum

const index = [1, 2, 3, 4, 5, 6, 7, 8, 9].findIndex(runningSum(25))

console.log(index)

answered Nov 15 '18 at 13:23

Yury Tarabanko

30.9k64668

Predicate has to be a function. MDN. But you could always create a function that returns another function.

const runningSum = (sum, current = 0) => value => (current += value) > sum

const index = [1, 2, 3, 4, 5, 6, 7, 8, 9].findIndex(runningSum(25))

console.log(index)

const runningSum = (sum, current = 0) => value => (current += value) > sum

const index = [1, 2, 3, 4, 5, 6, 7, 8, 9].findIndex(runningSum(25))

console.log(index)

const runningSum = (sum, current = 0) => value => (current += value) > sum

const index = [1, 2, 3, 4, 5, 6, 7, 8, 9].findIndex(runningSum(25))

console.log(index)

answered Nov 15 '18 at 13:23

Yury Tarabanko

30.9k64668

answered Nov 15 '18 at 13:23

Yury Tarabanko

30.9k64668

answered Nov 15 '18 at 13:23

Yury Tarabanko

30.9k64668

answered Nov 15 '18 at 13:23

Yury Tarabanko

30.9k64668

add a comment |

function predicate(max) 
 var sum = 0;
 return function(elem) 
 sum += elem;
 return sum > max;
 ;


const pred = predicate(25);

const index = arr.findIndex(pred);

answered Nov 15 '18 at 13:25

Bergi

377k63574903

add a comment |

function predicate(max) 
 var sum = 0;
 return function(elem) 
 sum += elem;
 return sum > max;
 ;


const pred = predicate(25);

const index = arr.findIndex(pred);

answered Nov 15 '18 at 13:25

Bergi

377k63574903

add a comment |

function predicate(max) 
 var sum = 0;
 return function(elem) 
 sum += elem;
 return sum > max;
 ;


const pred = predicate(25);

const index = arr.findIndex(pred);

answered Nov 15 '18 at 13:25

Bergi

377k63574903

function predicate(max) 
 var sum = 0;
 return function(elem) 
 sum += elem;
 return sum > max;
 ;


const pred = predicate(25);

const index = arr.findIndex(pred);

answered Nov 15 '18 at 13:25

Bergi

377k63574903

answered Nov 15 '18 at 13:25

Bergi

377k63574903

answered Nov 15 '18 at 13:25

Bergi

377k63574903

answered Nov 15 '18 at 13:25

Bergi

377k63574903

add a comment |

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