此函数如何从数组中删除所有伪造的值？

Question

function bouncer( arr ){
return arr.filter( function( value ){
    return value;
});

This function removes all falsy values from an array. I don't understand how it works. Does filter automatically only return non-falsy values?

Answer 1

Because filter calls the callback with each value from the array, and builds a new array that includes only the values for which filter returned a truthy value. So returning the value from the callback only retains truthy values (non-falsy ones), because when the callback returns a falsy value, filter leaves that entry out of the array it builds.

For details on how filter works, see MDN (readable) or the specification (markedly less so, but definitive).

Answer 2

You could use Boolean as well for filtering truthy values.

It returns a boolean value for every value.

The value passed as the first parameter is converted to a boolean value, if necessary. If the value is omitted or is 0 , -0 , null , false , NaN , undefined , or the empty string ( "" ), the object has an initial value of false . If the DOM object document.all is passed as a parameter, the new boolean object also has an initial value of false . All other values, including any object or the string "false" , create an object with an initial value of true .

function bouncer(arr) {
    return arr.filter(Boolean);
}