var

来源： https://stackoverflow.com/questions/12855000/bash-redirecting-eof-into-variable

来源： https://stackoverflow.com/questions/12855000/bash-redirecting-eof-into-variable

问题 This question already has answers here : Multiple join conditions using the $lookup operator (4 answers) Closed 2 years ago . I'd like to "join" 3 Collections in MongoDB by using mongochef. The collections are "Order", "Employee" and "City". I tried to use temp collections, but it is not effective. Now I am using var = a for the first "join". If I 'd like to show "a", there are displayed 20 results only. Do you have an idea or another solution? var a = db.Order.aggregate([ { $lookup: { from:

问题 This question already has answers here : Multiple join conditions using the $lookup operator (4 answers) Closed 2 years ago . I'd like to "join" 3 Collections in MongoDB by using mongochef. The collections are "Order", "Employee" and "City". I tried to use temp collections, but it is not effective. Now I am using var = a for the first "join". If I 'd like to show "a", there are displayed 20 results only. Do you have an idea or another solution? var a = db.Order.aggregate([ { $lookup: { from:

问题 Please note this is not duplicate of existing var vs let scope. I'm aware of the scope of var and let declarations and differences. But below scenario I could not justify with the understanding I had with let and var difference. In the below code, function foo accepts argument by name 'x' which has implicit let scope - as I cannot redeclare same variable name using let inside that function (uncommenting last line in function foo will throw JS error) "use strict"; function foo(x) { console.log

问题 Please note this is not duplicate of existing var vs let scope. I'm aware of the scope of var and let declarations and differences. But below scenario I could not justify with the understanding I had with let and var difference. In the below code, function foo accepts argument by name 'x' which has implicit let scope - as I cannot redeclare same variable name using let inside that function (uncommenting last line in function foo will throw JS error) "use strict"; function foo(x) { console.log

问题 Please note this is not duplicate of existing var vs let scope. I'm aware of the scope of var and let declarations and differences. But below scenario I could not justify with the understanding I had with let and var difference. In the below code, function foo accepts argument by name 'x' which has implicit let scope - as I cannot redeclare same variable name using let inside that function (uncommenting last line in function foo will throw JS error) "use strict"; function foo(x) { console.log

问题 This question already has answers here : Why let and var bindings behave differently using setTimeout function? [duplicate] (2 answers) Closed 2 years ago . I understand that let has block scope and var has functional scope. But I do not understand in this case, how using let will solve the problem const arr = [1,2,3,4]; for (var i = 0; i < arr.length; i++) { setTimeout(function() { console.log(arr[i]) }, 1000); } // Prints undefined 5 times const arr = [1,2,3,4]; for (let i = 0; i < arr

问题 A friend of mine noticed that var<Integer> list = new ArrayList<Double>(); was valid in Java. It turns out that the type of list is evaluated to ArrayList<Double> . When using var<Integer> list = new ArrayList<>(); , list is just ArrayList<Object> . Both of us were not able to figure out, what the generic type of var does, as it seems to be ignored. But if so, why is this even syntactically correct in the first place? 回答1: This is indeed a bug, but the proof lies in the Java Language

问题 console.log(a) //output:ƒ a(){} var a = 1; function a(){}; var a = 10; console.log(a) //output:10 ==================== var a = 1; if(true){ function a(){}; var a = 10; } console.log(a) // this code throws Uncaught SyntaxError: Identifier 'a' has already been declared both above code snippets are same except the if block.why does the latter throws error when its permissible in javascript to delcare same variable twice in the same scope with var as below function a(){}; var a = 10; //no error